U.S. patent number 9,787,605 [Application Number 14/814,473] was granted by the patent office on 2017-10-10 for logical router with multiple routing components.
This patent grant is currently assigned to NICIRA, Inc.. The grantee listed for this patent is Nicira, Inc.. Invention is credited to Ganesan Chandrashekhar, Kai-Wei Fan, Sreeram Ravinoothala, Ronghua Zhang.
United States Patent |
9,787,605 |
Zhang , et al. |
October 10, 2017 |
Logical router with multiple routing components
Abstract
Some embodiments provide a method for implementing a logical
router in a network. The method receives a definition of a logical
router for implementation on a set of network elements. The method
defines several routing components for the logical router. Each of
the defined routing components includes a separate set of routes
and separate set of logical interfaces. The method implements the
several routing components in the network. In some embodiments, the
several routing components include one distributed routing
component and several centralized routing components.
Inventors: |
Zhang; Ronghua (San Jose,
CA), Chandrashekhar; Ganesan (Campbell, CA),
Ravinoothala; Sreeram (San Jose, CA), Fan; Kai-Wei (San
Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nicira, Inc. |
Palo Alto |
CA |
US |
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Assignee: |
NICIRA, Inc. (Palo Alto,
CA)
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Family
ID: |
56553456 |
Appl.
No.: |
14/814,473 |
Filed: |
July 30, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160226754 A1 |
Aug 4, 2016 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62110061 |
Jan 30, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
45/64 (20130101); H04L 12/66 (20130101); H04L
69/329 (20130101); H04L 45/586 (20130101); H04L
45/742 (20130101); H04L 41/145 (20130101); H04L
45/02 (20130101); H04L 67/1002 (20130101); H04L
43/08 (20130101); H04L 45/122 (20130101); H04L
49/25 (20130101); H04L 45/306 (20130101); H04L
47/19 (20130101); H04L 61/2585 (20130101); H04L
67/1038 (20130101); H04L 45/74 (20130101); H04L
67/2842 (20130101); H04L 12/4654 (20130101); H04L
45/44 (20130101); H04L 49/9068 (20130101); H04L
43/106 (20130101); H04L 45/745 (20130101); H04L
49/3063 (20130101); H04L 12/4633 (20130101); H04L
49/354 (20130101); H04L 49/3009 (20130101); H04L
41/0654 (20130101); H04L 45/72 (20130101); H04L
69/321 (20130101); H04L 45/42 (20130101); H04L
41/5041 (20130101); H04L 67/327 (20130101); H04L
69/326 (20130101); H04L 45/38 (20130101); H04L
61/103 (20130101); H04L 61/6063 (20130101); H04L
2012/4629 (20130101); H04L 61/2503 (20130101); H04L
41/5077 (20130101); H04L 67/1095 (20130101); H04L
45/22 (20130101); H04L 45/28 (20130101) |
Current International
Class: |
H04W
4/00 (20090101); H04L 12/947 (20130101); H04L
29/08 (20060101); H04L 12/66 (20060101); H04L
12/26 (20060101); H04L 12/721 (20130101); H04L
12/935 (20130101); H04L 12/861 (20130101); H04L
12/741 (20130101); H04L 12/713 (20130101); H04L
12/931 (20130101); H04L 12/751 (20130101); H04L
12/717 (20130101); H04L 12/24 (20060101); H04L
12/733 (20130101); H04L 29/12 (20060101); H04L
12/801 (20130101); H04L 12/715 (20130101); H04L
12/707 (20130101) |
Field of
Search: |
;370/328-339,389-409 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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PCT/US2016/015778 |
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Jan 2016 |
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WO |
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PCT/US2016/015778 |
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Apr 2016 |
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WO |
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WO 2016/123550 |
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Aug 2016 |
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WO |
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Other References
Fernando, Cisco, R., et al., "Service Chaining using Virtual
Networks with BGP," Internet Engineering Task Force, IETF, Jul. 7,
2015, pp. 1-32, Internet Society (ISOC), Geneva, Switzerland,
available at
https://tools.ietf.org/html/draft-fm-bess-service-chaining-01.
cited by applicant .
International Search Report and Written Opinion of
PCT/US2016/015778, Jun. 24, 2016 (mailing date), Nicira, Inc. cited
by applicant .
Agarwal, Sugam, et al., "Traffic Engineering in Software Defined
Networks," 2013 192. Proceedings IEEE INFOCOM, Apr. 14, 2013, pp.
2211-2219, Bell Labs, Alcatel-Lucent, Holmdel, NJ, USA. cited by
applicant .
Lowe, Scott, "Learning NSX, Part 14: Using Logical Routing,"
Scott's Weblog: The weblog of an IT pro specializing in
virtualization, networking, open source, and cloud computing, Jun.
20, 2014, 8 pages, available at
http://blog.scottlowe.org/2014/06/20/learning-nsx-part-14-using-logical-r-
outing/. cited by applicant.
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Primary Examiner: Zaidi; Iqbal
Attorney, Agent or Firm: Adeli LLP
Claims
We claim:
1. A method for implementing a logical router in a network, the
method comprising: at a set of network controllers, receiving a
definition of a logical router for implementation by a set of
network elements, the definition of the logical router comprising
specification of a plurality of interfaces for connecting with an
external network; defining a plurality of routing components for
the logical router, each of the defined routing components
comprising a separate set of routes and separate set of logical
interfaces, wherein defining the plurality of routing components
comprises: assigning a first one of the plurality of interfaces to
a first gateway machine and a second one of the plurality of
interfaces to a second gateway machine; defining a first
centralized routing component for implementation on the first
gateway machine by defining (i) a first interface for the first
centralized routing component using configuration details of the
first interface assigned to the first gateway machine and (ii) a
second interface for the first centralized routing component used
to communicate with a distributed routing component; and defining a
second centralized routing component for implementation on the
second gateway machine by defining (i) a first interface for the
second centralized routing component using configuration details of
the second interface assigned to the second gateway machine and
(ii) a second interface for the second centralized routing
component used to communicate with the distributed routing
component; and generating data for configuring the set of network
elements to implement the plurality of routing components of the
logical router in the network.
2. The method of claim 1, wherein the plurality of routing
components comprises the distributed routing component and a
plurality of centralized routing components that includes at least
the first and second centralized routing components.
3. The method of claim 2 further comprising automatically defining
a logical switch for logically handling traffic between the
distributed routing component and the plurality of centralized
routing components.
4. The method of claim 3, wherein implementing the plurality of
routing components in the network comprises implementing each of
the centralized routing components on a single machine and
implementing the distributed routing component and logical switch
across a plurality of machines.
5. The method of claim 1, wherein each interface comprises a
network address and a data link address.
6. The method of claim 5, wherein network address data for the
first interface of the first centralized routing component is based
on network address data for the first one of the plurality of
interfaces and network address data for the second interface of the
first centralized routing component is generated separately from
any configuration details of the definition of the logical
router.
7. The method of claim 5, wherein the second interface of the first
centralized routing component and the second interface of the
second centralized routing component have different network
addresses and different data link layer addresses.
8. The method of claim 5, wherein the second interface of the first
centralized routing component and the second interface of the
second centralized routing component have a same network address
and different data link layer addresses.
9. The method of claim 1, wherein defining the plurality of routing
components further comprises defining a logical switch with ports
to which the second interface of the first centralized routing
component, the second interface of the second centralized routing
component, and an interface of the distributed routing component
all couple.
10. The method of claim 1, wherein the definition of the logical
router is received through an application programming interface
(API).
11. The method of claim 1, wherein the logical router is a first
logical router, the method further comprising receiving a
definition of a second logical router that connects to an interface
of the first logical router.
12. The method of claim 11, wherein the second logical router only
communicates with the external network through the first logical
router.
13. The method of claim 12 further comprising defining a single
distributed routing component for the second logical router when no
stateful services are configured for the second logical router.
14. The method of claim 12 further comprising defining (i) a
distributed routing component and (ii) two centralized routing
components for the second logical router when stateful services are
configured for the second logical router, each of the defined
routing components for the second logical router comprising a
separate set of routes and a separate set of logical
interfaces.
15. The method of claim 14 further comprising defining a logical
switch with ports to which an interface of each of the two
centralized routing components and a single interface of a
distributed routing component of the first logical router
couple.
16. The method of claim 14, wherein a first of the two centralized
routing components of the second logical router is designated as
active and a second of the two centralized routing components of
the second logical router is designated as standby, wherein the
first centralized routing component of the second logical router
responds to ARP requests and the second centralized routing
component of the second logical router does not respond to ARP
requests.
17. A non-transitory machine readable medium storing a network
controller program which when executed by at least one processing
unit implements a logical router in a network, the program
comprising sets of instructions for: at the network controller,
receiving a definition of a logical router for implementation by a
set of network elements, the definition of the logical router
comprising specification of a plurality of interfaces for
connecting with an external network; defining a plurality of
routing components for the logical router, each of the defined
routing components comprising a separate set of routes and separate
set of logical interfaces, wherein defining the plurality of
routing components comprises: assigning a first one of the
plurality of interfaces to a first gateway machine and a second one
of the plurality of interfaces to a second gateway machine;
defining a first centralized routing component for implementation
on the first gateway machine by defining (i) a first interface for
the first centralized routing component using configuration details
of the first interface assigned to the first gateway machine and
(ii) a second interface for the first centralized routing component
used to communicate with a distributed routing component; and
defining a second centralized routing component for implementation
on the second gateway machine by defining (i) a first interface for
the second centralized routing component using configuration
details of the second interface assigned to the second gateway
machine and (ii) a second interface for the second centralized
routing component used to communicate with the distributed routing
component; and generating data for configuring the set of network
elements to implement the plurality of routing components of the
logical router in the network.
18. The machine readable medium of claim 17, wherein the plurality
of routing components comprises the distributed routing component
and a plurality of centralized routing components that includes at
least the first and second centralized routing components, the
program further comprising a set of instructions for automatically
defining a logical switch for logically handling traffic between
the distributed routing component and the plurality of centralized
routing components, wherein the set of instructions for
implementing the plurality of routing components in the network
comprises a set of instructions for implementing each of the
centralized routing components on a single machine and implementing
the distributed routing component and logical switch across a
plurality of machines.
19. The machine readable medium of claim 17, wherein each interface
comprises a network address and a data link address.
20. The machine readable medium of claim 19, wherein network
address data for the first interface of the first centralized
routing component is based on network address data for the first
one of the plurality of interfaces and network address data for the
second interface of the first centralized routing component is
generated separately from any configuration details of the
definition of the logical router.
21. The machine readable medium of claim 17, wherein the set of
instructions for defining the plurality of routing components
further comprises a set of instructions for defining a logical
switch with ports to which the second interface of the first
centralized routing component, the second interface of the second
centralized routing component, and an interface of the distributed
routing component all couple.
22. The machine readable medium of claim 17, wherein the logical
router is a first logical router, the program further comprising a
set of instructions for receiving a definition of a second logical
router that connects to an interface of the first logical router,
wherein the second logical router only communicates with the
external network through the first logical router.
23. The machine readable medium of claim 22, wherein the program
further comprises a set of instructions for defining a single
distributed routing component for the second logical router when no
stateful services are configured for the second logical router.
24. The machine readable medium of claim 22, wherein the program
further comprises a set of instructions for defining (i) a
distributed routing component and (ii) two centralized routing
components for the second logical router when stateful services are
configured for the second logical router, each of the defined
routing components for the second logical router comprising a
separate set of routes and a separate set of logical
interfaces.
25. The machine readable medium of claim 24, wherein the program
further comprises a set of instructions for defining a logical
switch with ports to which an interface of each of the two
centralized routing components and a single interface of a
distributed routing component of the first logical router couple.
Description
BACKGROUND
Typical physical networks contain several physical routers to
perform L3 forwarding (i.e., routing). When a first machine wants
to send a packet to a second machine located on a different IP
subnet, the packet is sent to a router that uses a destination IP
address of the packet to determine through which of its physical
interfaces the packet should be sent. Larger networks will contain
multiple routers, such that if one of the routers fails, the
packets can be routed along a different path between the first
machine and the second machine.
In logical networks, user-defined data compute nodes (e.g., virtual
machines) on different subnets may need to communicate with each
other as well. In this case, tenants may define a network for
virtualization that includes both logical switches and logical
routers. Methods for implementing the logical routers to adequately
serve such virtualized logical networks in datacenters are
needed.
BRIEF SUMMARY
Some embodiments provide a method for implementing a logical router
in a network (e.g., in a datacenter). In some embodiments, the
method is performed by a management plane that centrally manages
the network (e.g., implemented in a network controller). The
method, in some embodiments, receives a definition of a logical
router (e.g., through an application programming interface (API)
and defines several routing components for the logical router. Each
of these routing components is separately assigned a set of routes
and a set of logical interfaces.
In some embodiments, the several routing components defined for a
logical router includes one distributed routing component and
several centralized routing components. In addition, the management
plane of some embodiments defines a logical switch for handling
communications between the components internal to the logical
router (referred to as a transit logical switch). The distributed
routing component and the transit logical switch are implemented in
a distributed manner by numerous machines within the datacenter,
while the centralized routing components are each implemented on a
single machine. Some embodiments implement the distributed
components in the datapath of managed forwarding elements on the
various machines, while the centralized routing components are
implemented in VMs (or other data compute nodes) on their single
machines. Other embodiments also implement the centralized
components in the datapath of their assigned machine.
The centralized components, in some embodiments, may be configured
in active-active or active-standby modes. In active-active mode,
all of the centralized components are fully functional at the same
time, and traffic can ingress or egress from the logical network
through the centralized components using equal-cost multi-path
(ECMP) forwarding principles (balancing the traffic across the
various centralized components). In this mode, each of the separate
centralized components has its own network layer (e.g., IP) address
and data link layer (e.g., MAC) address for communicating with an
external network. In addition, each of the separate centralized
components has its own network layer and data link layer address
for connecting to the transit logical switch in order to send
packets to and receive packets from the distributed routing
component.
In some embodiments, the logical router is part of a two-tier
logical network structure. The two-tier structure of some
embodiments includes a single logical router for connecting the
logical network to a network external to the datacenter (referred
to as a provider logical router (PLR) and administrated by, e.g.,
the owner of the datacenter), and multiple logical routers that
connect to the single logical router and do not separately
communicate with the external network (referred to as a tenant
logical router (TLR) and administrated by, e.g., different tenants
of the datacenter). Some embodiments implement the PLR in
active-active mode whenever possible, and only use active-standby
mode when stateful services (e.g., NAT, firewall, load balancer,
etc.) are configured for the logical router.
For the PLR, some embodiments enable route exchange with the
external network. Each of the centralized components of the PLR
runs a dynamic routing protocol process to advertise prefixes of
the logical network and receive routes towards the external
network. Through a network control system of network controllers
located both centrally in the datacenter and on the machines that
implement the logical network, these routes are propagated to the
other centralized components and the distributed routing component.
Some embodiments use different administrative metrics in the
routing information base (RIB) of the centralized component for
routes learned directly from the external network and routes
learned from a different peer centralized component that learned
the routes from the external network. Thus, a centralized component
will prefer routes that it learned directly to routes that involve
redirection through peer centralized components of the logical
router. However, when the different centralized components have
interfaces that are configured with different L3 connectivity
towards the external network, some embodiments create dummy
interfaces on the centralized components that are used to redirect
packets processed by a first centralized component through a second
centralized component to the external network.
In active-standby mode, on the other hand, only one of the
centralized components is fully operational at a time (the active
component), and only this component sends out messages to attract
traffic. In some embodiments, the two components use the same
network layer address (but different data link layer addresses) for
communicating with the distributed component, and only the active
component replies to address resolution protocol (ARP) requests
from this distributed component. Furthermore, only the active
centralized component advertises routes to the external network to
attract traffic.
When the logical router is a TLR, some embodiments either use no
centralized components or two centralized components in
active-standby mode when stateful services are configured for the
logical router. The TLR operates internally in the same manner as
the PLR in active-standby mode, with each of the two centralized
components having the same network layer address, and only the
active component responding to ARP requests. To connect to the PLR,
some embodiments also assign each of the two components a same
network layer address (though different from the address used to
connect to its own distributed component. In addition, the
management plane defines a transit logical switch between the
distributed component of the PLR and the centralized components of
the TLR.
In some cases, whether in active-active or active-standby mode, one
(or more) of the centralized router components will fail. This
failure may occur due to the machine on which the component
operates crashing completely, the data compute node or datapath
software that implements the machine corrupting, the ability of the
component to connect to either the external network or through
tunnels to other components of the logical network failing, etc.
When the failed component is a standby in active-standby mode, no
action need be taken in some embodiments. Otherwise, when one of
the centralized components fails, one of its peer components
becomes responsible for taking over its communications.
In active-standby mode, the standby centralized router component is
responsible for taking over for the failed active centralized
router component. To do so, if the logical router is a PLR, the new
active component begins advertising routes to the external network
so as to attract traffic from the external network (the failed
component, if its connectivity to the external network remains, is
responsible for stopping its own route advertisement so as to avoid
attracting this traffic). In addition, the new active component
sends messages (e.g., gratuitous ARP (GARP) replies) to the
distributed routing component of the PLR that it is now responsible
for the network layer address shared between the two components. If
the logical router is a TLR, this same set of GARP replies are
sent. In addition, to attract traffic from the PLR to which it
connects, the new active component sends GARP replies to the
transit logical switch that connects it to the PLR.
For the active-active mode of some embodiments, the management
plane designates all of the centralized components for a logical
router with a ranking at the time they are created. This ranking is
then used to determine which of the peer components will take over
for a failed component. Specifically, in some embodiments the
centralized component with the next-highest ranking to that of the
failed component takes over for the failed component. To take over,
the overtaking component identifies the network layer address of
the failed component that communicates with the distributed
component for the logical router, and sends GARP replies
associating its own data link layer address with the network layer
address of the failed component.
The preceding Summary is intended to serve as a brief introduction
to some embodiments of the invention. It is not meant to be an
introduction or overview of all inventive subject matter disclosed
in this document. The Detailed Description that follows and the
Drawings that are referred to in the Detailed Description will
further describe the embodiments described in the Summary as well
as other embodiments. Accordingly, to understand all the
embodiments described by this document, a full review of the
Summary, Detailed Description and the Drawings is needed. Moreover,
the claimed subject matters are not to be limited by the
illustrative details in the Summary, Detailed Description and the
Drawing, but rather are to be defined by the appended claims,
because the claimed subject matters can be embodied in other
specific forms without departing from the spirit of the subject
matters.
BRIEF DESCRIPTION OF THE DRAWINGS
The novel features of the invention are set forth in the appended
claims. However, for purpose of explanation, several embodiments of
the invention are set forth in the following figures.
FIG. 1 illustrates a configuration view of a logical router, which
represents a logical network as designed by a user.
FIG. 2 illustrates a management plane view of the logical network
of FIG. 1 when the logical router is implemented in a centralized
manner.
FIG. 3 illustrates a physical centralized implementation of the
logical router of FIG. 1.
FIG. 4 illustrates a management plane view of the logical network
of FIG. 1 when the logical router is implemented in a distributed
manner.
FIG. 5 illustrates a physical distributed implementation of the
logical router of FIG. 1.
FIG. 6 conceptually illustrates a logical network with two tiers of
logical routers.
FIG. 7 illustrates the management plane view for the logical
topology of FIG. 6 when a TLR in the logical network is completely
distributed.
FIG. 8 illustrates the management plane view for the logical
topology of FIG. 6 when the TLR in the logical network has a
centralized component.
FIG. 9 conceptually illustrates a more detailed configuration of a
logical network topology, including the network addresses and
interfaces assigned by an administrator.
FIG. 10 illustrates the configuration of the logical topology of
FIG. 9 by the management plane.
FIG. 11 conceptually illustrates a process of some embodiments for
configuring a PLR based on a user specification.
FIG. 12 conceptually illustrates a process of some embodiments for
configuring a TLR based on a user specification.
FIG. 13 conceptually illustrates a physical implementation of the
management plane constructs for the two-tiered logical network
shown in FIG. 8, in which the TLR and the PLR both include SRs as
well as a DR.
FIGS. 14A-B illustrate examples of traffic that egresses from the
logical network (northbound traffic) and ingresses to the logical
network (southbound traffic), respectively, for a logical topology
with a single tier of logical routers.
FIGS. 15A-B illustrate examples of northbound and southbound
traffic for a two-tier logical topology, with no centralized
services provided in the lower (TLR) tier.
FIGS. 16A-B illustrate examples of northbound and southbound
traffic for a two-tier logical topology with centralized services
provided in the lower (TLR) tier by SRs.
FIG. 17 conceptually illustrates the various stages of SR
processing of some embodiments.
FIGS. 18 and 19 illustrate a single-tier logical network topology
and the management plane view of that topology that meets the
requirements for the use of ECMP.
FIG. 20 illustrates a management plane view of the logical network
topology of FIG. 18 when the logical router is configured in
active-standby mode, rather than active-active (ECMP) mode.
FIG. 21 illustrates an example physical implementation of three
gateway machines that host the three reSRs for a particular
PLR.
FIG. 22 conceptually illustrates the result of one of the VMs that
implements one of the SRs of FIG. 21 crashing.
FIG. 23 conceptually illustrates the result of complete tunnel
failure at an MFE on the gateway machine that hosts one of the SRs
of FIG. 21.
FIG. 24 conceptually illustrates a process performed by a SR in
case of failover of a peer SR.
FIG. 25 conceptually illustrates an electronic system with which
some embodiments of the invention are implemented.
DETAILED DESCRIPTION
Some embodiments provide a two-tier logical router topology for
implementation in, e.g., a datacenter. These tiers include a top
tier of a provider logical router (PLR) and a lower tier of tenant
logical routers (TLR), in some embodiments. The two-tiered
structure enables both the provider (e.g., datacenter owner) and
the tenant (e.g., datacenter customer, often one of many such
customers) control over their own services and policies. In some
embodiments, the PLR layer is the logical layer that interfaces
with external physical networks, and therefore dynamic routing
protocols (e.g., BGP) may be configured on the PLR to enable the
exchange of routing information with physical routers outside the
datacenter. Some embodiments also allow the configuration of
bidirectional forwarding detection (BFD) or similar protocols for
monitoring whether physical network routers are up. Some
datacenters may not have multiple tenants, in which case the need
for separate PLR and TLRs is removed. In such cases, some
embodiments use a single-tier logical router topology, with the
single tier having the functionality of PLRs. The two-tier logical
topology of some embodiments is described in greater detail in U.S.
patent application Ser. No. 14/222,557, filed Mar. 21, 2014, now
published as U.S. Patent Publication 2015/0271303, which is
incorporated herein by reference.
In some embodiments, both PLRs and TLRs have the ability to support
stateless services (e.g., access control lists (ACLs)) as well as
stateful services (e.g., firewalls). In addition, logical switches
(to which data compute nodes such as VMs may couple) may connect to
either a PLR or a TLR. Furthermore, both PLRs and TLRs can be
implemented in either a distributed manner (e.g., with the logical
router processing performed in first-hop MFEs that physically
couple directly to the data compute nodes) or a centralized manner
(with the logical router processing performed in gateways for both
north-south and east-west traffic). For centralized
implementations, as well as for the centralized gateways by which
PLRs interact with the physical network even when implemented in a
distributed manner, both tiers of logical routers may be scaled out
by using multiple physical boxes in order to provide additional
throughput (e.g., using equal-cost multi-path (ECMP) techniques) as
well as for failure protection.
In some embodiments, the logical routers may only use stateful
services if implemented at least partially in a centralized (e.g.,
clustered) manner (to avoid the need for state-sharing between the
logical router implementations). In different embodiments, these
gateways (that provide centralized aspects of logical routers, as
well as which form the connection to the external network for
distributed PLRs) may be implemented as virtual machines (sometimes
referred to as Edge VMs), in other types of data compute nodes
(e.g., namespaces), or by using the Linux-based datapath
development kit (DPDK) packet processing software (e.g., as a VRF
in the DPDK-based datapath).
The following introduces some of the terminology and abbreviations
used in the specification: VNI (Virtual/Logical Network
Identifier)--a unique identifier (e.g., a 24-bit identifier) for a
logical domain (e.g., a logical switch) PLR (Provider Logical
Router--introduced above, a logical router over which a service
provider (e.g., datacenter operator) has full control; interfaces
directly with an external physical network. TLR (Tenant Logical
Router)--a logical router over which a tenant (e.g., a datacenter
customer, a group within an enterprise, etc.) has full control;
connects to a PLR to access an external physical network.
Distributed Logical Router--a logical router that supports
first-hop routing; that is, the logical router is implemented in
the managed forwarding elements to which the data compute nodes
directly couple. Centralized Logical Router--a logical router that
does not support first hop-routing Service Router (SR)--part of the
realization of a logical router that is used to provide centralized
services; in some embodiments, the SR is not exposed to the network
manager APIs except for troubleshooting purposes. Distributed
Router (DR)--part of the realization of a logical router used to
provide first-hop routing; in some embodiments, the DR is also not
exposed to the network manager APIs except for troubleshooting
purposes. Uplink--refers to both (i) the northbound interface of a
logical router (directed towards the external physical network) and
(ii) a team of pNICs of a gateway. Logical switch--a logical L2
broadcast domain. Transit logical switch--a logical switch created
automatically by the network manager to connect SRs/DR of a TLR
with the DR of a DR; in some embodiments, a transit logical switch
has no data compute nodes (e.g., customer workload VMs) connected
to it; furthermore, in some embodiments, the transit logical switch
is not exposed to the network manager APIs except for
troubleshooting purposes Context--a datapath representation of a
logical router; in some embodiments, the context may be a VRF, a
namespace, or a VM Transport Node, or Gateway--a node that
terminates tunnels defined by the network manager; in various
embodiments, may be a hypervisor-implemented virtual switch or a
DPDK-based Edge Node; in some embodiments, transport node may be
used interchangeably with datapath. Deployment Container (DC), or
Edge Cluster--a collection of homogeneous nodes, the uplinks of
which share the same L2 connectivity; in some embodiments, all
nodes in a DC are of the same type and belong to the same failure
domain. Edge Node--a node in a DC; may be a DPDK-based Edge or a
hypervisor-implemented virtual switch
The above introduces the concept of a two-tiered logical router
configuration as well as certain aspects of the logical router
configuration and implementation of some embodiments. In the
following, Section I focuses on the overall high-level design of
the logical router of some embodiments, while Section II describes
the configuration of the various logical router components. Section
III then describes the packet processing through the various
pipelines of some embodiments. Next, Section IV describes ECMP
processing in the active-active configuration, while Section V
describes the active-standby configuration. Section VI then
describes failover scenarios for the SRs. Finally, Section VII
describes the electronic system with which some embodiments of the
invention are implemented.
I. Logical Router and Physical Implementation
The following discussion describes the design of logical routers
for some embodiments as well as the implementation of such logical
routers by the network controllers of some embodiments. As
mentioned above, the logical routers of some embodiments are
designed such that they can be implemented in either a distributed
or centralized manner, they can scale out with or without stateful
(or stateless) services, and so that such services may be provided
by either a VRF context in a datapath or by a virtual machine
context.
Logical routers, in some embodiments, exist in three different
forms. The first of these forms is the API view, or configuration
view, which is how the logical router is defined by a user, such as
a datacenter provider or tenant (i.e., a received definition of the
logical router). The second view is the control plane, or
management plane, view, which is how the network controller
internally defines the logical router. Finally, the third view is
the physical realization, or implementation of the logical router,
which is how the logical router is actually implemented in the
datacenter.
In the control plane view, the logical router of some embodiments
may include one or both of a single DR and one or more SRs. The DR,
in some embodiments, spans managed forwarding elements (MFEs) that
couple directly to VMs or other data compute nodes that are
logically connected, directly or indirectly, to the logical router.
The DR of some embodiments also spans the gateways to which the
logical router is bound. The DR, as mentioned above, is responsible
for first-hop distributed routing between logical switches and/or
other logical routers that are logically connected to the logical
router. The SRs of some embodiments are responsible for delivering
services that are not implemented in a distributed fashion (e.g.,
some stateful services).
A. Centralized Logical Router
FIGS. 1-3 illustrate the three different views of a centralized
logical router implementation. FIG. 1 specifically illustrates the
configuration view, which represents a logical network 100 as
designed by a user. As shown, the logical router 115 is part of a
logical network 100 that includes the logical router 115 and two
logical switches 105 and 110. The two logical switches 105 and 110
each have VMs that connect to logical ports. While shown as VMs in
these figures, it should be understood that other types of data
compute nodes (e.g., namespaces, etc.) may connect to logical
switches in some embodiments. The logical router 115 also includes
two ports that connect to the external physical network 120.
FIG. 2 illustrates the management plane view 200 of the logical
network 100. The logical switches 105 and 110 are the same in this
view as the configuration view, but the network controller has
created two service routers 205 and 210 for the logical router 115.
In some embodiments, these SRs operate in active-standby mode, with
one of the SRs active and the other operating as a standby (in case
of the failure of the active SR). Each of the logical switches 105
and 110 has a connection to each of the SRs 205 and 210. If the
logical network 100 included three logical switches, then these
three logical switches would each connect to both of the SRs 205
and 210.
Finally, FIG. 3 illustrates the physical centralized implementation
of the logical router 100. As shown, each of the VMs that couples
to one of the logical switches 105 and 110 in the logical network
100 operates on a host machine 305. The MFEs 310 that operate on
these host machines are virtual switches (e.g., OVS, ESX) that
operate within the hypervisors or other virtualization software on
the host machines. These MFEs perform first-hop switching for the
logical switches 105 and 110 for packets sent by the VMs of the
logical network 100. The MFEs 310 (or a subset of them) also may
implement logical switches (and distributed logical routers) for
other logical networks if the other logical networks have VMs that
reside on the host machines 305 as well.
The two service routers 205 and 210 each operate on a different
gateway machine 315 and 320. The gateway machines 315 and 320 are
host machines similar to the machines 305 in some embodiments, but
host service routers rather than user VMs. In some embodiments, the
gateway machines 315 and 320 each include an MFE as well as the
service router, in order for the MFE to handle any logical
switching necessary. For instance, packets sent from the external
network 120 may be routed by the service router implementation on
the gateway and then subsequently switched by the MFE on the same
gateway.
The SRs may be implemented in a namespace, a virtual machine, or as
a VRF in different embodiments. The SRs may operate in an
active-active or active-standby mode in some embodiments, depending
on whether any stateful services (e.g., firewalls) are configured
on the logical router. When stateful services are configured, some
embodiments require only a single active SR. In some embodiments,
the active and standby service routers are provided with the same
configuration, but the MFEs 310 are configured to send packets via
a tunnel to the active SR (or to the MFE on the gateway machine
with the active SR). Only if the tunnel is down will the MFE send
packets to the standby gateway.
B. Distributed Logical Router
While the above section introduces a centralized implementation for
a logical router, some embodiments use distributed logical router
implementations that enable first-hop routing, rather than
concentrating all of the routing functionality at the gateways. In
some embodiments, the physical realization of a distributed logical
router always has a DR (i.e., the first-hop routing). A distributed
logical router will have SRs if either (i) the logical router is a
PLR, and therefore connects to external physical networks or (ii)
the logical router has services configured that do not have a
distributed implementation (e.g., NAT, load balancing, DHCP in some
embodiments). Even if there are no stateful services configured on
a PLR, some embodiments use SRs in the implementation to help with
failure handling in the case of ECMP.
FIGS. 4 and 5 illustrate, respectively, the management plane view
and physical implementation for a distributed logical router. The
configuration view entered by the user is the same as that shown in
FIG. 1 for a centralized router, with the difference being that the
user (e.g., administrator) denotes that the logical router will be
distributed. The control plane view 400 for the distributed
implementation illustrates that, in addition to the two service
routers 405 and 410, the control plane creates a distributed router
415 and a transit logical switch 420. The configuration of the
northbound and southbound interfaces of the various router
constructs 405-415 and their connections with the transit logical
switch 420 will be described in further detail below. In some
embodiments, the management plane generates separate routing
information bases (RIBs) for each of the router constructs 405-415.
That is, in addition to having separate objects created in the
management/control plane, each of the router constructs 405 is
treated as a separate router with separate routes. The transit
logical switch 420 then has logical ports for each of these
routers, and each of the router constructs has an interface to the
transit logical switch.
FIG. 5 illustrates the physical distributed implementation of the
logical router 100. As in the centralized implementation, each of
the VMs that couples to one of the logical switches 105 and 110 in
the logical network 100 operates on a host machine 505. The MFEs
510 perform first-hop switching and routing for the logical
switches 105 and 110 and for the logical router 115 (in addition to
performing switching and/or routing for other logical networks). As
shown in FIG. 5, the distributed router 415 is implemented across
the MFEs 510 as well as gateways 515 and 520. That is, the
datapaths (e.g., in the MFEs 510, in a similar MFE in the gateways
515 and 520 or in a different form factor on the gateways) all
include the necessary processing pipelines for the DR 415 (and the
transit logical switch 420). The packet processing of some
embodiments will be described in greater detail below.
C. Multi-Tier Topology
The previous examples illustrate only a single tier of logical
router. For logical networks with multiple tiers of logical
routers, some embodiments may include both DRs and SRs at each
level, or DRs and SRs at the upper level (the PLR tier) with only
DRs at the lower level (the TLR tier). FIG. 6 conceptually
illustrates a multi-tier logical network 600 of some embodiments,
with FIGS. 7 and 8 illustrating two different management plane
views of the logical networks.
FIG. 6 conceptually illustrates a logical network 600 with two
tiers of logical routers. As shown, the logical network 600
includes, at the layer 3 level, a provider logical router 605,
several tenant logical routers 610-620. The first tenant logical
router 610 has two logical switches 625 and 630 attached, with one
or more data compute nodes coupling to each of the logical
switches. For simplicity, only the logical switches attached to the
first TLR 610 are shown, although the other TLRs 615-620 would
typically have logical switches attached (to which data compute
nodes couple).
In some embodiments, any number of TLRs may be attached to a PLR
such as the PLR 605. Some datacenters may have only a single PLR to
which all TLRs implemented in the datacenter attach, whereas other
datacenters may have numerous PLRs. For instance, a large
datacenter may want to use different PLR policies for different
tenants, or may have too many different tenants to attach all of
the TLRs to a single PLR. Part of the routing table for a PLR
includes routes for all of the logical switch domains of its TLRs,
so attaching numerous TLRs to a PLR creates several routes for each
TLR just based on the subnets attached to the TLR. The PLR 605, as
shown in the figure, provides a connection to the external physical
network 635; some embodiments only allow the PLR to provide such a
connection, so that the datacenter provider can manage this
connection. Each of the separate TLRs 610-620, though part of the
logical network 600, are configured independently (although a
single tenant could have multiple TLRs if they so chose).
FIGS. 7 and 8 illustrate different possible management plane views
of the logical network 600, depending on whether or not the TLR 605
includes a centralized component. In these examples, the routing
aspects of the TLR 605 are always distributed using a DR. However,
if the configuration of the TLR 605 includes the provision of
stateful services, then the management plane view of the TLR (and
thus the physical implementation) will include active and standby
SRs for these stateful services.
Thus, FIG. 7 illustrates the management plane view 700 for the
logical topology 600 when the TLR 605 is completely distributed.
For simplicity, only details of the first TLR 610 are shown; the
other TLRs will each have their own DR, as well as SRs in some
cases. As in FIG. 4, the PLR 605 includes a DR 705 and three SRs
710-720, connected together by a transit logical switch 725. In
addition to the transit logical switch 725 within the PLR 605
implementation, the management plane also defines separate transit
logical switches 730-740 between each of the TLRs and the DR 705 of
the PLR. In the case in which the TLR 610 is completely distributed
(FIG. 7), the transit logical switch 730 connects to a DR 745 that
implements the configuration of the TLR 610. Thus, as will be
described in greater detail below, a packet sent to a destination
in the external network by a data compute node attached to the
logical switch 625 will be processed through the pipelines of the
logical switch 625, the DR 745 of TLR 610, the transit logical
switch 730, the DR 705 of the PLR 605, the transit logical switch
725, and one of the SRs 710-720. In some embodiments, the existence
and definition of the transit logical switches 725 and 730-740 are
hidden from the user that configures the network through the API
(e.g., an administrator), with the possible exception of
troubleshooting purposes.
FIG. 8 illustrates the management plane view 800 for the logical
topology 600 when the TLR 605 has a centralized component (e.g.,
because stateful services that cannot be distributed are defined
for the TLR). In some embodiments, stateful services such as
firewalls, NAT, load balancing, etc. are only provided in a
centralized manner. Other embodiments allow for some or all of such
services to be distributed, however. As with the previous figure,
only details of the first TLR 610 are shown for simplicity; the
other TLRs may have the same defined components (DR, transit LS,
and two SRs) or have only a DR as in the example of FIG. 7). The
PLR 605 is implemented in the same manner as in the previous
figure, with the DR 705 and the three SRs 710, connected to each
other by the transit logical switch 725. In addition, as in the
previous example, the management plane places the transit logical
switches 730-740 between the PLR and each of the TLRs.
The partially centralized implementation of the TLR 610 includes a
DR 805 to which the logical switches 625 and 630 attach, as well as
two SRs 810 and 815. As in the PLR implementation, the DR and the
two SRs each have interfaces to a transit logical switch 820. This
transit logical switch serves the same purposes as the switch 725,
in some embodiments. For TLRs, some embodiments implement the SRs
in active-standby manner, with one of the SRs designated as active
and the other designated as standby. Thus, so long as the active SR
is operational, packets sent by a data compute node attached to one
of the logical switches 625 and 630 will be sent to the active SR
rather than the standby SR.
The above figures illustrate the management plane view of logical
routers of some embodiments. In some embodiments, an administrator
or other user provides the logical topology (as well as other
configuration information) through an API. This data is provided to
a management plane, which defines the implementation of the logical
network topology (e.g., by defining the DRs, SRs, transit logical
switches, etc.). In addition, in some embodiments a user associates
each logical router (e.g., each PLR or TLR) with a set of physical
machines (e.g., a pre-defined group of machines in the datacenter)
for deployment. For purely distributed routers, such as the TLR 605
as implemented in FIG. 7, the set of physical machines is not
important, as the DR is implemented across the managed forwarding
elements that reside on hosts along with the data compute nodes
that connect to the logical network. However, if the logical router
implementation includes SRs, then these SRs will each be deployed
on specific physical machines. In some embodiments, the group of
physical machines is a set of machines designated for the purpose
of hosting SRs (as opposed to user VMs or other data compute nodes
that attach to logical switches). In other embodiments, the SRs are
deployed on machines alongside the user data compute nodes.
In some embodiments, the user definition of a logical router
includes a particular number of uplinks. Described herein, an
uplink is a northbound interface of a logical router in the logical
topology. For a TLR, its uplinks connect to a PLR (all of the
uplinks connect to the same PLR, generally). For a PLR, its uplinks
connect to external routers. Some embodiments require all of the
uplinks of a PLR to have the same external router connectivity,
while other embodiments allow the uplinks to connect to different
sets of external routers. Once the user selects a group of machines
for the logical router, if SRs are required for the logical router,
the management plane assigns each of the uplinks of the logical
router to a physical machine in the selected group of machines. The
management plane then creates an SR on each of the machines to
which an uplink is assigned. Some embodiments allow multiple
uplinks to be assigned to the same machine, in which case the SR on
the machine has multiple northbound interfaces.
As mentioned above, in some embodiments the SR may be implemented
as a virtual machine or other container, or as a VRF context (e.g.,
in the case of DPDK-based SR implementations). In some embodiments,
the choice for the implementation of an SR may be based on the
services chosen for the logical router and which type of SR best
provides those services.
In addition, the management plane of some embodiments creates the
transit logical switches. For each transit logical switch, the
management plane assigns a unique VNI to the logical switch,
creates a port on each SR and DR that connects to the transit
logical switch, and allocates an IP address for any SRs and the DR
that connect to the logical switch. Some embodiments require that
the subnet assigned to each transit logical switch is unique within
a logical L3 network topology having numerous TLRs (e.g., the
network topology 600), each of which may have its own transit
logical switch. That is, in FIG. 8, transit logical switch 725
within the PLR implementation, transit logical switches 730-740
between the PLR and the TLRs, and transit logical switch 820 (as
well as the transit logical switch within the implementation of any
of the other TLRs) each require a unique subnet. Furthermore, in
some embodiments, the SR may need to initiate a connection to a VM
in logical space, e.g. HA proxy. To ensure that return traffic
works, some embodiments avoid using link local IP addresses.
Some embodiments place various restrictions on the connection of
logical routers in a multi-tier configuration. For instance, while
some embodiments allow any number of tiers of logical routers
(e.g., a PLR tier that connects to the external network, along with
numerous tiers of TLRs), other embodiments only allow a two-tier
topology (one tier of TLRs that connect to the PLR). In addition,
some embodiments allow each TLR to connect to only one PLR, and
each logical switch created by a user (i.e., not a transit logical
switch) is only allowed to connect to one PLR or one TLR. Some
embodiments also add the restriction that southbound ports of a
logical router must each be in different subnets. Thus, two logical
switches may not have the same subnet if connecting to the same
logical router. Lastly, some embodiments require that different
uplinks of a PLR must be present on different gateway machines. It
should be understood that some embodiments include none of these
requirements, or may include various different combinations of the
requirements.
II. SR and DR Configuration
When a user configures a logical router, this configuration is used
by the management plane to configure the SRs and DR for the logical
router. For instance, the logical router 115 of FIG. 1 has four
interfaces (two to the logical switches, and two uplinks). However,
its distributed management plane implementation in FIG. 4 includes
a DR with three interfaces and SRs with two interfaces each (a
total of seven interfaces). The IP and MAC addresses and other
configuration details assigned to the four interfaces as part of
the logical router configuration are used to generate the
configuration for the various components of the logical router.
In addition, as part of the configuration, some embodiments
generate a routing information base (RIB) for each of the logical
router components. That is, although the administrator defines only
a single logical router, the management plane and/or control plane
of some embodiments generates separate RIBs for the DR and for each
of the SRs. For the SRs of a PLR, in some embodiments the
management plane generates the RIB initially, but the physical
implementation of the SR also runs a dynamic routing protocol
process (e.g., BGP, OSPF, etc.) to supplement the RIB locally.
Some embodiments include several types of routes in the RIB of a
logical routers, and therefore in the RIBs of its component
routers. All routes, in some embodiments, include administrative
distance values, used to determine priority, with larger values
indicating lower priority types of route (i.e., if two routes exist
for the same prefix, the one with a lower distance value is used).
If multiple routes for the same prefix are in the RIB with the same
distance value, traffic to these prefixes is spread across the
different routes (e.g., using ECMP principles to balance the
traffic evenly). connected (0): prefixes configured on the logical
router's ports static (1): configured by the administrator/user
management plane internal (10): default routes--when a TLR is
connected to a PLR, a default route pointing to the PLR is added to
the RIB of the TLR; when a logical switch is connected to a TLR,
the user allows the subnet to be redistributed, and the subnet is
not NAT'ed, a default route pointing to the TLR for the subnet is
added to the RIB of the PLR EBGP (20): the next four types are
routes learned through dynamic routing protocols OSPF internal (30)
OSPF external (110) IBGP (200).
It should be understood that not all logical routers will include
both BGP and OSPF routes in some embodiments, and some logical
routers may include neither. For instance, a logical router that
does not include a connection to external networks may not use any
routing protocol, and some logical routers may run only one type of
route-sharing protocol, rather than both BGP and OSPF.
In addition, in some embodiments, the SRs of the PLRs (that use the
dynamic routing protocols) merge the RIB received from the
centralized controllers (containing static, connected, and
management plane internal routes) with the routes learned from the
physical routers (via the dynamic routing protocols). The SR
locally calculates its FIB based on the incorporation of these
dynamic routes in order to expedite route convergence, rather than
sending the learned routes back to the centralized controller for
recalculation. For the DRs, the centralized controllers of some
embodiments pushes down the entire RIB, with a local control plane
calculating the FIB.
A. DR Configuration
In some embodiments, the DR is always located on the southbound
side (i.e., facing the data compute nodes of the logical network,
rather than facing the external physical network) of the logical
router implementation. Unless the logical router has no centralized
component, the uplinks of the logical router will not be configured
for the DR, whose northbound interfaces instead couple to the
transit logical switch that is part of the logical router.
FIG. 9 conceptually illustrates the more detailed configuration of
a logical network topology 900, including the network addresses and
interfaces assigned by an administrator. As shown, the logical
switches 905 and 910 are each assigned their own subnets,
1.1.1.0/24 and 1.1.2.0/24, and all of the data compute nodes
attached to the logical switches 905 will have IP addresses in the
corresponding subnet. The logical router 915 has an interface L1 to
the first logical switch 905, with an IP address of 1.1.1.253 that
is the default gateway for the data compute nodes in the subnet
1.1.1.0/24. The logical router 915 also has a second interface L2
to the second logical switch 910, with an IP address of 1.1.2.253
that is the default gateway for the data compute nodes in the
subnet 1.1.2.0/24.
The northbound side of the logical router 915 has two uplinks, U1
and U2. The first uplink U1 has an IP address of 192.168.1.252 and
connects to a first physical router 920 with an IP address of
192.168.1.252. The second uplink U2 has an IP address of
192.168.2.253 and connects to a second physical router 925 with an
IP address of 192.168.2.252. The physical routers 920 and 925 are
not actually part of the logical network, but rather connect the
logical network to the external network. Though in the illustrated
case each of the uplinks connects to a single, different physical
router, in some cases each of the uplinks will connect to the same
set of several physical routers. That is, both U1 and U2 might both
connect to both of the physical routers 920 and 925. Some
embodiments require that each of the external routers to which the
uplinks connect provide the same connectivity, although this is not
the case in the illustrated example. Instead, the first physical
router 920 connects to the subnet 10.0.0.0/8, while the second
router 925 connects to both the subnet 10.0.0.0/8 and
11.0.0.0/8.
For a logical router with a distributed component, some embodiments
configure the DR as follows. The southbound interfaces are
configured in the same way as the southbound interfaces of the
logical router. These interfaces are those that connect to a
logical switch in the logical topology, or to a lower-level logical
router (e.g., the southbound interfaces of a PLR may connect to
TLRs). The DR of some embodiments is allocated a single northbound
interface, which is assigned an IP address and a MAC address.
Assuming the logical router has one or more SRs, the northbound
interface of the DR connects to a transit logical switch.
The RIB of the DR is assigned connected routes based on the subnets
configured on its various southbound and northbound interfaces.
These are the subnets configured for (i) the transit logical switch
configured between the DR and SR components of the logical router,
and (ii) any logical switches on its southbound interfaces. These
logical switches on the southbound interfaces may be user-defined
logical domains to which data compute nodes connect, or transit
logical switches located between the DR of a PLR and any TLRs that
connect to the PLR.
In addition, any static routes that egress from an uplink of the
logical router are included in the RIB of the DR; however, these
routes are modified such that the next-hop IP address is set to
that of the uplink's SR. For example, a static route "a.b.c.0/24
via 192.168.1.252" (192.168.1.252 being an address of an external
physical network router) is modified to be "a.b.c.0/24 via [IP of
SR southbound interface]". Static routes that egress from a
southbound interface of the logical router, on the other hand, are
included in the RIB of the DR unmodified. In some embodiments, for
each SR of the logical router, a default route of the type
management plane internal is added to the RIB of the DR. Instead,
in other embodiments, dynamic routes learned by a particular SR are
added to the RIB, with the next-hop IP address modified to be the
IP of the southbound interface of the particular SR. This is an
alternative to the default route, because the management plane
internal type would otherwise have a higher priority than the
dynamic routes learned by the SR. However, for TLRs, the SRs do not
run a dynamic routing protocol in some embodiments, so the default
route with a next-hop IP address pointing to the interface of the
active SR is used instead.
FIG. 10 illustrates the configuration 1000 of the logical topology
900 by the management plane. As shown, the logical switches 905 and
910 are configured as indicated by the user configuration. As in
the previous examples, the logical router 915 includes a DR 1005,
two SRs 1010 and 1015, and a transit logical switch 1020. The DR is
assigned the two southbound interfaces of the logical router 905,
which connect to the logical switches 905 and 910. The transit
logical switch is assigned a subnet of 192.168.100.0/24, which
needs to satisfy the requirement that it be unique among the
logical switches that logically connect (directly or indirectly) to
the logical router 905. Each of the three management plane router
constructs 1005-1015 also includes an interface that connects to
the transit logical switch, and has an IP address in the subnet of
the transit logical switch. The northbound interfaces U1 and U2 are
assigned to the two SRs 1010 and 1015, the configuration of which
is described below.
Using the rules of some embodiments described above for generating
the RIB, the RIB of the DR 1005 includes the following routes:
1.1.1.0/24 output to L1 1.1.2.0/24 output to L2 192.168.100.0/24
output to DRP1 192.168.1.0/24 via IP1 192.168.2.0/24 via IP2
10.0.0.0/8 via IP1 10.0.0.0/8 via IP2 11.0.0.0/8 via IP2 0.0.0.0/0
via IP1 0.0.0.0/0 via IP2
The above routes include three connected routes, for the logical
switch domains connected to the DR (1.1.1.0/24, 1.1.2.0/24, and
192.168.100.0/24). In addition, the subnet on which the first
uplink is located (192.168.1.0/24) is reached via the southbound
interface of the first SR 1010 (IP1), while the subnet on which the
second uplink is located (192.168.2.0/24) is reached via the
southbound interface of the second SR 1015 (IP2). In addition,
three static routes have been added by the user for the logical
router 915, which the management plane automatically modifies for
the DR 1005. Specifically, the routes include the network
10.0.0.0/8 via the southbound interface of either of the SRs, and
the network 11.0.0.0/8 via the southbound interface of SR2. Lastly,
default routes pointing to these same southbound interfaces are
included. The IP addresses IP1, IP2, and IP3 that are created by
the management plane for the ports of the logical router constructs
that interface with the transit logical switch all are in the
subnet 192.168.100.0/24.
In addition to configuring the RIB of the DR, the management plane
also assigns MAC addresses to the DR interfaces in some
embodiments. In some embodiments, some or all of the physical
routing elements (e.g., software modules) in the physical network
that implement the DR functionality only support a single MAC
address. In this case, because the MAC of a DR port may come from
that of a logical router port visible to users, this imposes
requirements on how the management plane allocates MAC addresses
for the logical router ports. Thus, in some embodiments, all DR/SR
ports that connect to any logical switch which has user data
compute nodes or SRs connected must share a common MAC address. In
addition, if a DR/SR port is connected to another DR/SR or to a
physical network, this port is assigned a unique MAC address in
some embodiments (this assignment rule ignoress the transit logical
switch when determining whether a DR/SR port is connected to
another DR/SR port)
B. SR Configuration
As with the DR of a logical router, the management plane also
configures each SR of the logical router with a separate RIB and
interfaces. As described above, in some embodiments SRs of both
PLRs and TLRs may deliver services (i.e., functionalities beyond
simply routing, such as NAT, firewall, load balancing, etc.) and
the SRs for PLRs also provide the connection between the logical
network and external physical networks. In some embodiments, the
implementation of the SRs is designed to meet several goals. First,
the implementation ensures that the services can scale out--that
is, the services assigned to a logical router may be delivered by
any of the several SRs of the logical router. Second, some
embodiments configure the SR in such a way that the service
policies may depend on routing decisions (e.g., interface-based
NAT). Third, the SRs of a logical router have the ability to handle
failure (e.g., of the physical machine on which an SR operates, of
the tunnels to that physical machine, etc.) among themselves
without requiring the involvement of a centralized control plane or
management plane (though some embodiments allow the SRs to operate
at reduced capacity or in a suboptimal manner). Finally, the SRs
ideally avoid unnecessary redirecting amongst themselves. That is,
an SR should forward packets to the external physical network if it
has the ability do so locally, only forwarding the packet to a
different SR if necessary. Of course, the forwarding between SRs
should avoid packet loops.
As shown in FIG. 10, each SR has one southbound interface that
connects to the transit logical switch 1020 that resides between
the SRs and the DR. In addition, in some embodiments, each SR has
the same number of northbound interfaces as the logical router.
That is, even though only one uplink may be assigned to the
physical machine on which the SR operates, all of the logical
router interfaces are defined on the SR. However, some of these
interfaces are local interfaces while some of them are referred to
as dummy interfaces.
The local northbound interfaces, in some embodiments, are those
through which a packet can egress directly from the SR (e.g.,
directly to the physical network). An interface configured based on
the uplink (or one of the uplinks) assigned to the SR is a local
interface. On the other hand, an interface configured based on one
of the other uplinks of the logical router assigned to a different
SR is referred to as a dummy interface. Providing the SR with
configuration for the dummy interfaces allows for the first-hop
MFEs to send packets for any of the uplinks to any of the SRs, with
that SR able to process the packets even if the packet is not
destined for its local interface. Some embodiments, after
processing a packet at one of the SRs for a dummy interface,
forward the packet to the appropriate SR where that interface is
local, in order for the other SR to forward the packet out to the
external physical network. The use of dummy interfaces also allows
the centralized controller (or set of controllers) that manages the
network to push service policies that depend on routing decisions
to all of the SRs, thereby allowing services to be delivered by any
of the SRs.
As discussed below in Section IV, in some embodiments the SRs
exchange routing information with the physical network (e.g., using
a route advertisement protocol such as BGP or OSPF). One goal of
this route exchange is that irrespective of which SR routes a
packet towards the physical network, the routing decision should
always point to either a local interface of the SR or a dummy
interface that corresponds to an uplink of the logical router on a
different SR. Thus, the policies associated with the logical router
uplink can be applied by the SR even when the uplink is not
assigned to that SR, enabling the scale out of stateful services.
In some embodiments, the routes received from a peer SR will have a
larger distance value than routes learned directly from a physical
next-hop router, thereby ensuring that a SR will send a packet to
its peer SR only when it cannot send the packet directly to a
physical network router.
For a logical router that has one or more centralized components,
some embodiments configure the SR as follows. For northbound
interfaces, the SR has the same number of such interfaces as the
logical router, and these interfaces each inherit the IP and MAC
address of the corresponding logical router interfaces. A subset of
these interfaces are marked as local interfaces (those for which
the uplink is assigned to the SR), while the rest of the interfaces
are marked as dummy interfaces. In some embodiments, the service
policies defined for the logical router are pushed equivalently to
all of the SRs, as these are configured in the same way from the
network and interface perspective. The dynamic routing
configuration for a particular logical router port/uplink are
transferred to the local interface of the SR to which that
particular uplink is assigned.
Each SR, as mentioned, is assigned a single southbound interface
(also a local interface) that connects to a transit logical switch,
with each SR's southbound interface connecting to the same transit
logical switch. The IP addresses for each of these southbound
interfaces is in the same subnet as the northbound interface
assigned to the DR (that of the transit logical switch). Some
embodiments differentiate the assignment of IP addresses between
the SRs depending on whether the SRs are in active-active or
active-standby mode. For active-active mode (i.e., when all of the
SRs are treated as equals for routing purposes), different IP and
MAC addresses are assigned to the southbound interfaces of all of
the SRs. On the other hand, in active-standby mode, the same IP is
used for both of the southbound interfaces of the two SRs, while
each of the interfaces is assigned a different MAC address.
As indicated in the above subsection regarding DRs, users may
configure static routes for the logical router. A static route (or
a connected route) of the logical router that egresses from an
uplink is copied to the RIB of the SR. The distance metric for such
a route is unmodified if the uplink through which the route
egresses is assigned to the SR; however, if the uplink is a dummy
interface on the SR, then some embodiments add a value to this
metric so that the SR will prefer a route that egresses from its
local interface when the network can be reached without redirecting
the packet to a different SR through a dummy interface. In
addition, the SRs (of a top-level logical router) may learn dynamic
routes and place these in their RIB (though some embodiments
perform this locally, without involving the centralized
controllers). In some embodiments, the dynamic routes learned from
peer SRs are installed without this adjustment of the distance
metric, because by default the metric for routes learned from IBGP
(SR to SR peering) or OSPF are larger than the metric for routes
learned from EBGP.
For each southbound interface of the logical router, some
embodiments add a route for the corresponding network to the RIB of
each SR. This route points to the northbound DR interface as its
next-hop IP address. Furthermore, any other routes configured for
the logical router that egress from the southbound interface are
copied to the SR with the same northbound DR interface as the
next-hop IP address.
Returning to the example of FIG. 10, as the logical router 915 has
two uplinks, the management plane defines two service routers 1010
and 1015. The first service router 1010 has a local interface for
U1 and a dummy interface for U2, referred to as U2'. Similarly, the
second service router 1015 has a local interface for U2 and a dummy
interface, U1', for the first uplink U1. Each of these SRs is
assigned a southbound interface, with different IP and MAC
addresses (as the SRs are in an active-active configuration). The
IP addresses IP1 (for the first SR 1010) and IP2 (for the second SR
1015) are in the subnet 192.1.100.0/24, as is IP3 (the northbound
interface of the DR 1005).
Using the rules of some embodiments, and assuming the a routing
protocol (e.g., BGP) is enabled for the SRs, the RIB of the first
SR 1010 will include the following routes: 10.0.0.0/8 output to U1
via 192.168.1.252, metric 20 (via EBGP) 10.0.0.0/8 output to U2'
via 192.168.2.252, metric 200 (via IBGP) 11.0.0.0/8 output to U2'
via 192.168.2.252, metric 200 (via IBGP) 192.168.1.0/24 output to
U1, metric 0 (connected) 192.168.100.0/24 output to SRP1, metric 0
(connected) 1.1.1.0/24 via IP3, metric 10 (management plane
internal) 1.1.2.0/24 via IP3, metric 10 (management plane
internal)
Similarly, the RIB of the second SR 1015 will include the following
routes: 10.0.0.0/8 output to U2 via 192.168.2.252, metric 20 (via
EBGP) 10.0.0.0/8 output to U1' via 192.168.1.252, metric 200 (via
IBGP) 11.0.0.0/8 output to U2 via 192.168.2.252, metric 20 (via
EBGP) 192.168.2.0/24 output to U2, metric 0 (connected)
192.168.100.0/24 output to SRP2, metric 0 (connected) 1.1.1.0/24
via IP3, metric 10 (management plane internal) 1.1.2.0/24 via IP3,
metric 10 (management plane internal)
C. Management Plane Processes
FIG. 11 conceptually illustrates a process 1100 of some embodiments
for configuring a PLR based on a user specification. In some
embodiments, the process 1100 is performed by the management plane
(e.g., a set of modules at a centralized controller that manages
the networks of a datacenter). The management plane performs the
configuration process, then uses a centralized control plane of the
controller (or of a different network controller) to distribute the
data to various local control planes on the various host machines
that implement the configured logical router.
As shown, the process 1100 begins by receiving (at 1105) a
specification of a PLR. The specification of a PLR (or definition
of the PLR) is based on administrator input to define the PLR
(e.g., an administrator employed by the owner of the datacenter).
In some embodiments, this specification includes definitions of any
services the PLR should provide, whether the PLR will be configured
in active-active or active-standby mode (though some embodiments
automatically use active-active mode unless stateful services are
configured), how many uplinks are configured for the PLR, the IP
and MAC addresses of the uplinks, the L2 and L3 connectivity of the
uplinks, the subnets of any southbound interfaces of the PLR (one
interface if the PLR is intended for a two-tier topology, and any
number of interfaces if user logical switches will connect directly
in a single-tier topology), any static routes for the RIB of the
PLR, as well as other data. It should be understood that different
embodiments may include different combinations of the listed data
or other data in the configuration data for a PLR.
The process 1100 then defines (at 1110) a DR using this
configuration data. This assumes that the PLR will not be
completely centralized, in which case no DR is generated by the
management plane. For the southbound interface of the DR, the
management plane uses the southbound interface configuration of the
PLR. That is, the IP address and MAC address for the DR are those
specified for the logical router.
In addition, the process assigns (at 1115) each uplink specified
for the PLR to a gateway machine. As described above, some
embodiments allow (or require) the user to specify a particular set
of physical gateway machines for the location of the SRs of the
logical router. In some embodiments, the set of gateway machines
might be together within a particular rack or group of racks of
servers, or are otherwise related, with tunnels connecting all of
the machines in a set. The management plane then assigns each of
the uplinks to one of the gateway machines in the selected set.
Some embodiments allow multiple uplinks to be assigned to the same
gateway machine (so long as the logical router does not have only
two uplinks configured in active-standby mode), while other
embodiments only allow a single uplink per gateway machine for the
PLR irrespective of whether in active-active or active-standby.
After assigning the uplinks to gateway machines, the process 1100
defines (at 1120) a SR on each of the selected gateway machines.
For each SR, the process uses the configuration for the uplink
assigned to that gateway machine as the configuration for the
northbound interface of the SR. This configuration information
includes the IP and MAC address of the uplink, as well as any
uplink-specific policies. It should be understood that, for
situations in which different policies and/or L3 connectivity are
allowed and used between the different uplinks, some embodiments
also configure dummy interfaces on the SRs in order to redirect
packets if needed.
The process additionally defines (at 1125) a transit logical switch
to connect the defined SRs and DR. In some embodiments, the
management plane assigns a unique VNI (logical switch identifier)
to the transit logical switch. In addition, some embodiments
require that the subnet assigned to the transit logical switch be
unique among the logical network topology. As such, the transit
logical switch must use a subnet different from any user-defined
logical switches that interface directly with the PLR, as well as
all transit logical switches between the PLR and any TLRs that
connect to the PLR, all transit logical switches within these TLRs,
and any user-defined logical switches that connect to these
TLRs.
Next, the process 1100 assigns (at 1130) a northbound interface to
the DR. The northbound interface, in some embodiments, is assigned
both a MAC address and an IP address (used for packets sent
internally between the components of the PLR). In some embodiments,
the IP address is in the subnet that was assigned to the transit
logical switch defined at 1125. The configuration of the transit
logical switch includes an association of this MAC address with one
of its logical ports.
The process then determines (at 1135) whether the PLR is configured
in active-active mode (or active-standby mode). As noted above, in
some embodiments, this determination is made by the administrator
as part of the configuration settings for the PLR. In other
embodiments, the management plane automatically defines the SRs in
active-active configuration for PLRs unless stateful services are
set up, in which case the SRs are defined in active-standby
mode.
When the PLR is configured in active-standby mode, the process
assigns (at 1140) southbound interfaces of each of the two SRs (or
more than two SRs, if there are multiple standbys). In the
active-standby case, these southbound interfaces all have the same
IP address, which is in the subnet of the transit logical switch
defined at operation 1125. Although the two interfaces receive the
same IP address, some embodiments assign different MAC addresses,
so as to differentiate the two as destinations for northbound
packets routed by the DR. In other embodiments, the same MAC
addresses are used as well, with different mechanisms in the case
of failover used as described below.
The process then assigns (at 1145) one of the SRs as active and one
of the SRs as standby. Some embodiments make this determination
randomly, while other embodiments attempt to balance the assignment
of active and standby SRs across the gateway machines, as described
in greater detail in U.S. Patent Publication 2015/0063364, filed
Jan. 28, 2014, which is incorporated herein by reference. The SR
assigned as active will respond to ARP requests for the southbound
interface, and will advertise prefixes to the external physical
network from its northbound interface. The standby SR, on the other
hand, will not respond to ARP requests (so as to avoid receiving
northbound traffic), and will not advertise prefixes (but will
maintain a BGP session in order to receive routes from the external
network in case of failure of the active SR.
Lastly, the process 1100 generates (at 1150) separate RIBs for the
DR and for each of the SRs. The separate RIBs are generated based
on the configuration data in the manner described in the previous
subsections, as well as below in Section V. The process then ends.
In some embodiments, the management plane also calculates the FIB
centrally, while in other embodiments the local control planes
(operating on the host and gateway machines) performs the RIB
traversal to generate the FIB to use in actual forwarding of
packets by the logical router components. In either case, the RIB
is updated on the SRs based on the dynamic routes learned from the
external network, and that data is propagated to the DR via central
controllers. The calculation of the FIB by network controllers of
some embodiments is described in greater detail in U.S. patent
application Ser. No. 14/214,545, filed Mar. 17, 2014, now issued as
U.S. Pat. No. 9,313,129, which is incorporated herein by
reference.
On the other hand, when the PLR is configured in active-active
(ECMP) mode, the process assigns (at 1155) southbound interfaces of
each of the SRs. In the active-active cases, these southbound
interfaces are each assigned different IP addresses in the subnet
of the transit logical switch defined at operation 1125, as well as
different MAC addresses. With different IP addresses, each of the
SRs can handle northbound packets based on the IP address selected
for a given packet by the DR pipeline in a host machine.
Next, the process assigns (at 1160) ranks to the SRs. As described
in detail below, the SRs use the ranks in case of failover to
determine which SR will take over responsibilities for a failed SR.
In some embodiments, the next-highest ranked SR takes over for a
failed SR by taking over its southbound interfaces so as to attract
northbound traffic that would otherwise be sent to the IP address
of the failed SR.
Finally, the process generates (at 1165) separate RIBs for the DR
and for each of the SRs. The separate RIBs are generated based on
the configuration data in the manner described in the previous
subsections, as well as below in Section IV. The process then ends.
In some embodiments, the management plane also calculates the FIB
centrally, while in other embodiments the local control planes
(operating on the host and gateway machines) performs the RIB
traversal to generate the FIB to use in actual forwarding of
packets by the logical router components. In either case, the RIB
is updated on the SRs based on the dynamic routes learned from the
external network, and that data is propagated to the DR via central
controllers.
The above description of FIG. 11 indicates the operations of the
management plane to generate the various components for a PLR
(upper tier logical router). FIG. 12 conceptually illustrates a
process 1200 of some embodiments for configuring a TLR based on a
user specification. In some embodiments, the process 1200 is
performed by the management plane (e.g., a set of modules at a
centralized controller that manages the networks of a datacenter).
The management plane performs the configuration process, then uses
a centralized control plane of the controller (or a different
network controller) to distribute the data to various local control
planes on the various host machines that implement the configured
logical router.
As shown, the process begins by receiving (at 1205) a specification
of a TLR. The specification of a TLR (or definition of the TLR) is
based on administrator input to define the TLR (e.g., an
administrator employed by a tenant of the datacenter). In some
embodiments, this specification includes definitions of any
services the TLR should provide, which PLR the TLR should connect
to through its uplink, any logical switches that connect to the
TLR, IP and MAC addresses for the interfaces of the TLR, any static
routes for the RIB of the TLR, as well as other data. It should be
understood that different embodiments may include different
combinations of the listed data or other data in the configuration
data for the TLR.
The process 1200 then determines (at 1210) whether the TLR has a
centralized component. In some embodiments, if the TLR does not
provide stateful services, then no SRs are defined for the TLR, and
it is implemented only in a distributed manner. On the other hand,
some embodiments require SRs in active-standby mode when stateful
services are provided, as shown in this figure.
When the TLR does not provide stateful services or otherwise
require a centralized component, the process defines (at 1215) a DR
using the specification of the logical router for both the
southbound and northbound interfaces. The DR may have numerous
southbound interfaces, depending on how many logical switches are
defined to connect to the TLR. On the other hand, some embodiments
restrict TLRs to a single northbound interface that sends packets
to and receives packets from a PLR. The process also generates (at
1220) a RIB for the DR. The RIB for the DR will include all of the
routes for the logical router, generated as described above.
On the other hand, when the TLR provides stateful services or
requires a centralized component for other reasons, the process
defines (at 1225) a DR using the received configuration data. For
the southbound interfaces of the DR, the management plane uses the
southbound interface configurations of the TLR. That is, the IP
address and MAC address for each southbound interface are those
specified for the ports of the logical router to which the various
logical switches couple.
In addition, the process assigns (at 1230) the uplink specified for
the TLR to two gateway machines. While some embodiments allow TLRs
to operate in active-active mode with multiple uplinks, the process
1200 is for embodiments that restrict the TLRs to a single uplink
in active-standby mode. As described above, some embodiments allow
(or require) the user to specify a particular set of physical
gateway machines for the location of the SRs of the logical router.
In some embodiments, the set of gateway machines might be together
within a particular rack or group of racks of servers, or are
otherwise related, with tunnels connecting all of the machines in a
set. The management plane then assigns the uplink to two of the
gateway machines in the selected set.
After assigning the uplinks to gateway machines, the process 1200
defines (at 1235) a SR on each of the two gateway machines. For
each SR, the management plane uses the configuration for the single
uplink as the configuration for the northbound interface of the SR.
As there is only one northbound interface, the process applies the
same configuration to both of the SRs. That is, not only is the
same IP address used for both northbound interfaces, but the
services on the interfaces are configured in the same manner as
well. However, different MAC addresses are used for the northbound
interfaces, so as to differentiate the active and standby SRs.
The process additionally defines (at 1240) a transit logical switch
to connect the defined SRs and DR. In some embodiments, the
management plane assigns a unique VNI (logical switch identifier)
to the transit logical switch. In addition, some embodiments
require that the subnet assigned to the transit logical switch be
unique among the logical network topology. As such, the management
plane must assign the transit logical switch a subnet different
than any of the user-defined logical switches that interface with
the TLR, as well as any transit logical switches between the TLR
(or other TLRs) and the PLR, as well as all transit logical
switches within other TLRs that connect to the same PLR, the
transit logical switch within the PLR, and the user-defined logical
switches that connect to the other TLRs.
Next, the process assigns (at 1245) a northbound interface to the
DR. This interface, in some embodiments, is assigned both a MAC
address and an IP address (used for packets sent internally between
the components of the TLR). In some embodiments, the IP address is
in the same subnet that was assigned to the transit logical switch
at 1140. The process also assigns (at 1250) southbound interfaces
of each of the two SRs. As this is an active-standby configuration,
these southbound interfaces have the same IP address, which is in
the subnet of the transit logical switch defined at operation 1140.
Although the two interfaces receive the same IP address, some
embodiments assign different MAC addresses, so as to differentiate
the two as destinations for northbound packets routed by the DR. In
other embodiments, the same MAC addresses are used as well, with
different mechanisms in the case of failover used as described
below.
The process 1200 then assigns (at 1255) one of the SRs as active
and one of the SRs as standby. Some embodiments make this
determination randomly, while other embodiments attempt to balance
the assignment of active and standby SRs across the gateway
machines. The SR assigned as active will respond to ARP requests
for the southbound (from the DR of this TLR) and northbound (from
the DR of the PLR) interfaces. The standby SR, on the other hand,
will not respond to ARP requests (so as to avoid receiving
northbound or southbound traffic).
Next, the process generates (at 1260) separate RIBs for the DR and
for each of the SRs. The separate RIBs are generated based on the
configuration data in the manner described in the previous
subsections, as well as below in Section IV. In some embodiments,
the management plane also calculates the FIB centrally, while in
other embodiments the local control planes (operating on the host
and gateway machines) performs the RIB traversal to generate the
FIB to use in actual forwarding of packets by the logical router
components. In either case, the RIB is updated on the SRs based on
the dynamic routes learned from the external network, and that data
is propagated to the DR via central controllers.
Irrespective of whether the TLR is generated with or without SRs,
the process 1200 defines (at 1265) another transit logical between
the TLR and the PLR to which it connects. This transit logical
switch has a unique VNI, and a subnet to which the uplink IP
address of the TLR belongs. In addition, an interface on the DR of
the PLR is created in the same subnet to connect to the transit
logical switch. The process then ends.
It should be understood that while the processes 1100 and 1200
illustrate a specific order for performing these various
operations, these processes are merely conceptual. In various
different embodiments, the management plane may perform the actual
operations in various different orders, or even perform some of the
operations in parallel. For instance, the management plane could
define the transit logical switch first, prior to defining the SR
or DR at all, could define all of the logical router components
completely before assigning them to separate physical machines,
etc.
III. Packet Processing
The above sections describe the configuration of the various
logical router components by the management plane. These logical
router components (as well as the logical switches, both those
defined by the user and those defined by the management plane for
connecting logical router components) are implemented in the
datacenter by various managed forwarding elements (MFEs). As shown
in FIG. 5, for example, the data compute nodes attached to the
user-defined logical switches reside on physical host machines, on
which MFEs operate (e.g., within the virtualization software of the
host machine) as first-hop packet processing elements. These MFEs
implement the logical switches of a logical network as well as the
DRs, in some embodiments.
FIG. 13 conceptually illustrates a physical implementation of the
management plane constructs for a two-tiered logical network shown
in FIG. 8, in which the TLR 610 and the PLR 605 both include SRs as
well as a DR. It should be understood that this figure only shows
the implementation of the TLR 610, and not the numerous other TLRs,
which might be implemented on numerous other host machines, and the
SRs of which might be implemented on other gateway machines.
This figure assumes that there are two VMs attached to each of the
two logical switches 625 and 630, which reside on the four physical
host machines 1305-1320. Each of these host machines includes a MFE
1325. These MFEs may be flow-based forwarding elements (e.g., Open
vSwitch) or code-based forwarding elements (e.g., ESX), or a
combination of the two, in various different embodiments. These
different types of forwarding elements implement the various
logical forwarding elements differently, but in each case they
execute a pipeline for each logical forwarding element that may be
required to process a packet.
Thus, as shown in FIG. 13, the MFEs 1325 on the physical host
machines include configuration to implement both logical switches
625 and 630 (LSA and LSB), the DR 805 and transit logical switch
815 for the TLR 610, and the DR 705 and transit logical switch 725
for the PLR 605. Some embodiments, however, only implement the
distributed components of the PLR on the host machine MFEs 1325
(those that couple to the data compute nodes) when the TLR for a
data compute node residing on the host machine does not have a
centralized component (i.e., SRs). As discussed below, northbound
packets sent from the VMs to the external network will be processed
by their local (first-hop) MFE, until a transit logical switch
pipeline specifies to send the packet to a SR. If that first SR is
part of the TLR, then the first-hop MFE will not perform any PLR
processing, and therefore the PLR pipeline configuration need not
be pushed to these MFEs by the centralized controller(s). However,
because of the possibility that one of the TLRs 615-620 may not
have a centralized component, some embodiments always push the
distributed aspects of the PLR (the DR and the transit LS) to all
of the MFEs. Other embodiments only push the configuration for the
PLR pipelines to the MFEs that are also receiving configuration for
the fully distributed TLRs (those without any SRs).
In addition, the physical implementation shown in FIG. 13 includes
four physical gateway machines 1330-1345 (also called edge nodes,
in some embodiments) to which the SRs of the PLR 605 and the TLR
610 are assigned. In this case, the administrators that configured
the PLR 605 and the TLR 610 selected the same group of physical
gateway machines for the SRs, and the management plane assigned one
of the SRs for both of these logical routers to the third gateway
machine 1340. As shown, the three SRs 710-720 for the PLR 605 are
each assigned to different gateway machines 1330-1340, while the
two SRs 810 and 815 for the TLR 610 are also each assigned to
different gateway machines 1340 and 1345.
This figure shows the SRs as separate from the MFEs 1350 that
operate on the gateway machines. As indicated above, different
embodiments may implement the SRs differently. Some embodiments
implement the SRs as VMs (e.g., when the MFE is a virtual switch
integrated into the virtualization software of the gateway machine,
in which case the SR processing is performed outside of the MFE. On
the other hand, some embodiments implement the SRs as VRFs within
the MFE datapath (when the MFE uses DPDK for the datapath
processing). In either case, the MFE treats the SR as part of the
datapath, but in the case of the SR being a VM (or other data
compute node), sends the packet to the separate SR for processing
by the SR pipeline (which may include the performance of various
services). As with the MFEs 1325 on the host machines, the MFEs
1350 of some embodiments are configured to perform all of the
distributed processing components of the logical network.
A. Single-Tier Topology
The packet processing pipelines for various examples will now be
described. FIGS. 14A and 14B illustrate examples of traffic that
egresses from the logical network (northbound traffic) and
ingresses to the logical network (southbound traffic),
respectively, for a logical topology with a single tier of logical
routers. These figures illustrate a single tier topology 1400 with
a logical router 1405 (with a connection to external networks) and
two logical switches 1410 and 1415. As described above, the logical
router 1405 includes a DR 1420, two SRs 1425 and 1430, and a
transit logical switch 1435.
In some embodiments, east-west traffic (i.e., traffic from a data
compute node on LS1 to a data compute node on LS2 is handled
primarily at the first-hop MFE (e.g., the MFE of the virtualization
software on the host machine for the source data compute node),
then tunneled to the destination MFE. As such, the packets do not
pass through the SRs, and thus does not receive any services
provided by these SRs. Other embodiments, however, allow for
routing policies that send certain east-west traffic to the SRs for
processing.
As shown in FIG. 14A, when a VM or other data compute node on a
machine sends a northbound packet, the datapath on the MFE
initially runs the source logical switch pipeline (e.g., based on
the ingress port through which the packet is received, the source
MAC address, etc.). This pipeline specifies to forward the packet
to the DR 1420, the pipeline for which also takes place on the
source MFE. This pipeline identifies one of the SRs 1425 and 1430
as its next hop. In the active-standby case, the pipeline
identifies the active SR; in the active-active case, some
embodiments use ECMP to select one of the SRs, as described below.
Next, the source MFE executes the pipeline for the transit logical
switch 1435, which specifies to tunnel the packet to the
appropriate gateway machine (edge node) that hosts the selected SR.
The gateway machine (e.g., the MFE on the gateway machine) receives
the packet, decapsulates it (to remove the tunneling data), and
identifies the SR based on the logical context information on the
packet (e.g., the VNI of the transit logical switch 1435) as well
as the destination MAC address that corresponds to the SR's
southbound interface. The SR pipeline is then executed (by the MFE
in some embodiments, and by a VM implementing the SR in other
embodiments). The SR pipeline sends the packet to the physical
network. If the SR pipeline specifies a local interface, then the
packet is delivered directly to the physical network; on the other
hand, if the SR pipeline specifies a dummy interface, the packet
may be redirected through a tunnel to a different gateway machine
to which the specified interface is local.
FIG. 14B illustrates the packet processing for ingressing
(southbound) packets. The packet is received at one of the gateway
machines on which an SR operates. The MFE at the gateway machine
identifies the destination SR based on the VLAN and destination MAC
address of the incoming packet, and runs the SR pipeline (e.g.,
sends the packet to the VM on which the SR operates, or runs the
pipeline directly in the datapath, depending on how the SR is
implemented). The SR pipeline identifies the DR 1420 as its next
hop. The MFE then executes the transit logical switch 1435
pipeline, which forwards the packet to the DR, as well as the DR
pipeline, which routes the packet to its destination. The
destination logical switch pipeline (i.e., one of the logical
switches 1410 and 1415) is also executed, which specifies to tunnel
the packet to the MFE of the host machine on which the destination
VM resides. After decapsulating the packet, the destination MFE
delivers the packet to the VM.
B. Two-Tier Topology without Centralized Services in TLR
FIGS. 15A and 15B illustrate examples of northbound and southbound
traffic for a two-tier logical topology, with no centralized
services provided in the lower (TLR) tier. These figures illustrate
a two-tier topology 1500 with a PLR 1505 (with two uplinks to
external networks), a TLR 1510, and two logical switches 1515 and
1520. The PLR 1505 includes a DR 1525, two SRs 1530 and 1535, and
transit logical switch 1540 that connects the three components. The
TLR 1510 does not have centralized services configured, and
therefore only includes a single DR component 1545. Between the DR
1545 of the TLR and the DR 1525 of the PLR the management plane
inserts a second transit logical switch 1550.
The processing pipeline for the two-tier topology without stateful
services at the TLR level is similar to the single-tier topology
pipeline, but with additional pipelines executed at the first-hop
MFE. As shown in FIG. 15A, when a VM or other data compute node on
a machine sends a northbound packet, the datapath on the MFE of the
source machine initially runs the source logical switch pipeline
(e.g., based on the ingress port through which the packet is
received, the source MAC address, etc.). This pipeline specifies to
forward the packet to the DR 1545 of the TLR 1510, the pipeline for
which is also executed on the source (first-hop) MFE. This pipeline
identifies the southbound interface of the DR 1525 as its next-hop,
and the source MFE then executes the pipeline for the transit
logical switch 1550 interposed between the two DRs. This logical
switch pipeline logically forwards the packet to the DR port (the
upper-layer DR), and the source MFE then executes the pipeline for
the DR 1525 as well. This pipeline identifies one of the SRs 1530
and 1535 as the next hop for the packet. In the active-standby
case, the pipeline identifies the active SR; in the active-active
case, some embodiments use ECMP to select one of the SRs, as
described below.
Next, the source MFE executes the pipeline for the transit logical
switch 1540 internal to the PLR 1505, which specifies to tunnel the
packet to the appropriate gateway machine (edge node) that hosts
the selected SR (identified by the transit logical switch pipeline
based on MAC address, in some embodiments). The gateway machine
(e.g., the MFE on the gateway machine) receives the packet,
decapsulates it (to remove the tunneling encapsulation), and
identifies the SR based on the logical context information on the
packet (e.g., the VNI of the transit logical switch 1540) as well
as the destination MAC address that corresponds to the SR's
southbound interface. The SR pipeline is then executed (by the MFE
in some embodiments, and by a VM implementing the SR in other
embodiments). The SR pipeline sends the packet to the physical
network. If the SR pipeline specifies a local interface, then the
packet is delivered directly to the physical network; on the other
hand, if the SR pipeline specifies a dummy interface, the packet
may be redirected through a tunnel to a different gateway machine
to which the specified interface is local.
Southbound traffic is also handled similarly to the single-tier
case. As shown in FIG. 15B, a southbound packet is received at one
of the gateway machines on which an SR of the PLR 1505 operates.
The MFE at the gateway machine identifies the destination SR (some
embodiments allow the gateway machines to host numerous SRs for
various different logical routers) based on the VLAN and
destination MAC address of the incoming packet, and runs the SR
pipeline (e.g., sends the packet to the VM on which the SR
operates, or runs the pipeline directly in the datapath, depending
on how the SR is implemented). The SR pipeline identifies the DR
1525 as its next hop, so the MFE then executes the transit logical
switch 1540 pipeline, which forwards the packet to the DR 1525. The
DR 1525 pipeline identifies the TLR DR 1545 as its next hop, and
thus the MFE on the edge node also executes the pipeline of the
transit logical switch 1550 and subsequently, that of the DR 1545.
The lower-level DR pipeline routes the packet to its destination,
so the destination logical switch pipeline (i.e., one of the
logical switches 1515 and 1520) is also executed, which specifies
to tunnel the packet to the MFE of the host machine on which the
destination VM resides. After decapsulating the packet, the
destination MFE delivers the packet to the VM.
For east-west traffic, in some embodiments, the source MFE handles
all of the processing, as in the single-tier case. Within a TLR
(e.g., from a VM on the first logical switch 1513 to a VM on the
logical switch 1520, only the single DR pipeline (and the two
logical switch pipelines) needs to be executed. For packets sent
across TLRs, the source MFE executes all three of the DR pipelines
in some embodiments (so long as the destination TLR-DR and logical
switch pipelines are implemented on the source MFE. As in the
single-tier case, some embodiments allow east-west traffic to be
sent to the SRs on the gateway machines, while other embodiments do
not enable the centralized services for east-west traffic.
C. Two-Tier Topology with Centralized Services in TLR
Finally, FIGS. 16A and 16B illustrate examples of northbound and
southbound traffic for a two-tier logical topology with centralized
services provided in the lower (TLR) tier by SRs. These figures
illustrate a two-tier topology 1600 with a PLR 1605 (with two
uplinks to external networks), a TLR 1610 (with centralized
services), and two logical switches 1615 and 1620. The PLR 1605
includes a DR 1625, two SRs 1630 and 1635, and a transit logical
switch 1640 that connects the three components. The TLR also
includes a DR 1645, two SRs 1650 and 1655, and a transit logical
switch 1660 that connects its three components. The management
plane also has inserted a third transit logical switch 1665 between
the SRs 1650 and 1655 of the TLR 1610 and the DR 1625 of the PLR
1605.
Unlike the previous examples, in which nearly the entire packet
processing pipeline was performed at the first hop, packet
processing for the logical topology 1600 is spread across three
machines for both northbound and southbound traffic. As shown in
FIG. 16A, when a VM or other data compute node on a machine sends a
northbound packet, the datapath on the MFE of the source machine
initially runs the source logical switch pipeline, as in the
previous examples. This pipeline specifies to forward the packet to
the DR 1645 of the TLR 1610, the pipeline for which is also
executed on the source (first-hop) MFE. This DR pipeline identifies
the southbound interface of one of the SRs 1650 and 1655 as its
next hop IP address. In some embodiments, the TLR SRs are always
configured in active-standby mode, so the next hop is the same for
both of the SRs but the packet is routed to the MAC address of the
active SR.
The source MFE then executes the pipeline for the transit logical
switch 1660 internal to the TLR 1610, which specifies to tunnel the
packet to the appropriate gateway machine (edge node) that hosts
the selected SR of the TLR 1610 (which the transit logical switch
identifies based on the destination MAC address after routing by
the DR 1645 pipeline). The gateway machine (e.g., the MFE on the
gateway machine) receives the packet, decapsulates it, and
identifies the SR based on the logical context information on the
packet (e.g., the VNI of the transit logical switch 1660) as well
as the destination MAC address that corresponds to the SR's
southbound interface. The SR pipeline (including any of the
stateful services) is then executed (e.g., by the MFE or a VM
implementing the SR), which specifies the southbound interface of
the DR 1625 as its next hop address. The transit logical switch
1665 pipeline is executed on the current edge node (Edge Node 2 in
the figure), as is the DR pipeline of the PLR 1605. This DR
pipeline identifies one of the SRs 1630 and 1635 as the next hop
for the packet, in the same manner as described in the previous
examples.
The edge node MFE executes the pipeline for the transit logical
switch 1640 internal to the PLR 1605, which specifies to tunnel the
packet to the appropriate gateway machine that hosts the selected
SR 1630 or 1635 (identified by the transit logical switch pipeline
based on MAC address, in some embodiments). The gateway machine
(e.g., the MFE on the gateway machine) receives the packet,
decapsulates it (to remove the tunneling encapsulation), and
identifies the SR based on the logical context information on the
packet (e.g., the VNI of the transit logical switch 1640) as well
as the destination MAC address that corresponds to the SR's
southbound interface. The SR pipeline is then executed (by the MFE
in some embodiments, and by a VM implementing the SR in other
embodiments). The SR pipeline sends the packet to the physical
network. If the SR pipeline specifies a local interface, then the
packet is delivered directly to the physical network; on the other
hand, if the SR pipeline specifies a dummy interface, the packet
may be redirected through a tunnel to a different gateway machine
to which the specified interface is local.
Southbound traffic processing is also distributed across three
machines (unless the SR for the PLR 1605 and the SR for the TLR
1610 are located on the same gateway machine). As shown in FIG.
16B, a southbound packet is received at one of the gateway machines
on which an SR of the PLR 1605 operates. The MFE at the gateway
machine identifies the destination SR based on the VLAN and
destination MAC address of the incoming packet, and runs the SR
pipeline (e.g., sends the packet to the VM on which the SR
operates, or runs the pipeline directly in the datapath, depending
on how the SR is implemented). The SR pipeline identifies the DR
1625 as its next hop, so the MFE then executes the transit logical
switch 1640 pipeline, which forwards the packet to the DR 1625. The
DR 1625 pipeline identifies the northbound interface of one of the
SRs 1650 and 1655 of the TLR 1610 as its next hop. In the
active-standby case, the active SR is selected.
The MFE on the first gateway machine then executes the transit
logical switch 1665 pipeline, which specifies to tunnel the packet
to a second gateway machine (Edge Node 2) on which this second SR
that performs stateful services for the TLR 1610 is located. The
second gateway machine (e.g., the MFE on the second gateway
machine) decapsulates the packet and identifies the destination SR
based on the VNI and MAC address on the packet. The MFE runs the SR
pipeline (either in its datapath or by sending the packet to a VM
on the gateway machine), which identifies the DR 1645 as the next
hop. The MFE thus executes the transit logical switch 1660
pipeline, which forwards the packet to the DR 1645, and then
executes this DR pipeline as well. The DR pipeline routes the
packet to its destination, so the destination logical switch
pipeline (one of the logical switches 1615 and 1620) is executed,
and the packet is tunneled to the MFE of the host machine on which
the destination VM resides. After decapsulating the packet, the
destination MFE delivers the packet to the VM.
For east-west traffic within a TLR, the source logical switch, DR,
and destination logical switch pipelines are all executed at the
first-hop MFE, then the packet is tunneled to the destination MFE.
IF the packet requires processing by the centralized services, only
the source logical switch, DR, and transit logical switch pipelines
are performed at the first-hop MFE, with the SR pipeline, transit
logical switch (again), DR (again), and destination logical switch
pipelines performed by the gateway machine before tunneling the
packet to the destination. For cross-TLR traffic, the packet starts
out in the same way, with the first-hop MFE performing the source
logical switch, DR, and transit logical switch pipelines to select
a SR. The gateway machine on which the selected SR runs then
executes the SR pipeline to identify the DR of the PLR, the transit
logical switch pipeline between the TLR and the PLR, the DR of the
PLR pipeline (which identifies a next hop as a component of a
different TLR), and at least the transit logical switch between the
PLR and the destination TLR. If the destination TLR has only a DR,
then that pipeline is also executed at the first gateway machine,
along with the destination logical switch, before tunneling the
packet to its destination MFE. If the destination TLR has SRs, the
transit logical switch specifies to tunnel the packet to the
gateway machine for a selected SR of the destination TLR. That
second gateway machine executes the SR pipeline, the transit
logical switch pipeline internal to the destination TLR, the DR
pipeline for that TLR, and the destination logical switch pipeline,
before tunneling the packet to the destination MFE.
The same principle applies in all of the above cases, which is to
perform the processing pipelines as early as possible. Thus, all of
the pipelines for a given packet are performed at the first-hop MFE
(e.g., the hypervisor-based virtual switch that receives a packet
from a VM on that hypervisor), until the packet needs to be sent to
a SR pipeline only present on a specific gateway machine. That
gateway machine then performs all of the processing it can, until
the packet is sent out to a physical network or to a different
gateway machine (or to its destination for east-west traffic).
D. Additional Logical Router Behavior
Much like physical routers, logical routers are implemented to
perform typical routing functionalities such as decrementing the
time to live (TTL) for packets that it routes, and performing ARP.
In some embodiments, a logical router with both DR and SRs only
decrements a packet once, by the first component that acts upon the
packet. Thus, for northbound and east-west traffic, the DR
decrements the TTL, whereas the SR decrements the TTL for
southbound traffic. In some embodiments, the DR implementation has
instructions to only decrement TTL for packets received on its
southbound interface, and the SRs have similar instructions to only
decrement TTL for packets received on their northbound interfaces.
The component that handles decrementing the TTL for a packet also
handles generating an ICMP error message if the TTL is dropped to
zero.
The logical routers of some embodiments do not forward broadcast
packets, and thus do not support directed broadcast (a feature
typically disabled on physical routers as well). However, if an IP
broadcast packet is received on the logical network to which it is
addressed, the logical router of some embodiments treats itself as
a destination of the packet.
For ARP, in some embodiments, the logical router rewrites the MAC
address of the inner packet (i.e., the packet before a tunnel
encapsulation is appended to the packet) to indicate which
transport node is sending the ARP packet, so that the ARP response
is forwarded to the correct transport node. For the tunnel
encapsulation, some embodiments use stateless transport tunneling
(STT) along with VXLAN semantics.
E. Packet Processing by SR
The above descriptions describe the packet processing by the SR as
simply one additional logical forwarding element in the datapath
for a packet, which may not be implemented at the first hop (for
northbound or east-west packets, at least). However, where the
other logical forwarding elements (logical switches, DRs, transit
logical switches) basically involve ingress processing, logical
forwarding, and egress processing (the ingress and egress
processing may involve ACLs), the SR processing may include other
functions such as stateful services in addition to the
forwarding-related processing.
FIG. 17 conceptually illustrates the various stages of SR
processing 1700 of some embodiments. Some of these stages are only
included in the processing when the SR includes non-forwarding
services (e.g., NAT, stateful firewall, load balancing, etc.).
Thus, the diagram shows certain stages in dashed rather than solid
lines to indicate that the SR only performs these stages if
configured for services. In addition, the pre-service redirect
stage 1705 is illustrated using dotted lines to indicate that the
SR only performs this stage if the SR contains services and its
logical router is configured in active-active mode.
As shown, when a SR receives a packet (whether the SR is
implemented as a VM or as a VRF in a DPDK-based datapath), the
first stage 1705 is the pre-service redirect operation. As
mentioned, the SR only performs this stage if stateful services are
configured and the SRs are operating in active-active mode. The
pre-service redirect stage 1705 involves redirecting the packet to
the owner SR for a connection (e.g., a transport connection) to
which the packet belongs. However, if no services are configured on
the logical router, or the SR is operating in active-standby mode
(in which case all packets are sent to the active SR), then this
stage is not needed. In some embodiments, the pre-service redirect
stage does not decrement TTL (as the packet will be properly
decremented when routed at a later stage).
The pre-routing service stages 1710-1715 may involve any number of
stateful services configured on the SR for performance prior to
routing. The SR performs these stages upon determining that no
redirect is necessary or receiving a packet via redirect from a
different SR. Of course, if no stateful services are configured on
the SR, these operations will not be performed as well. Depending
on the configuration of the SR, and whether certain services
require the determination of an egress logical port of the logical
router, some services may be performed either before or after
routing.
After all the pre-routing services have been performed by the SR,
the SR then performs the routing stage 1720. As discussed above,
the routing tables for all of the SR instances will be similar. For
instance, if multiple SRs can reach the same network, then all SRs
will have multiple routes for that network, with routes that point
to a local interface having a smaller distance metric than routes
that point to a dummy interface, so the local interface will be
chosen when possible. The routing stage 1720 results in a routing
decision, which includes a next hop IP address and an egress
logical port of the logical router (in some embodiments, the egress
logical port may already be known based on routing performed by the
DR for northbound packets).
After being routed, the packet proceeds to the post-routing
services stages 1725-1730. These stages, like the pre-routing
services stages 1710-1715, are only performed by the SR if stateful
services are configured on the logical router. In some embodiments,
some or all of the post-routing service stages may depend on the
routing decision. For example, interface-based NAT configured for
the logical router may depend on the logical egress port. In
addition, some embodiments require that the post-routing services
do not alter the routing decision (though they may cause the SR to
drop the packet, in some cases).
Next, the SR processes the packet through the egress ACL stage
1735. At this stage, the SR enforces any security policies
configured for the logical egress port of the logical router. The
SR then ARPs (at stage 1740) the next hop to determine the new
destination MAC address for the packet. When the egress interface
of the SR is a dummy interface, in some embodiments the ARP is
injected into the destination L2 via proxy in the same way that the
DR performs ARP in the logical space. After ARP concludes, the SR
modifies the source and destination MAC addresses of the
packet.
Lastly, the packet proceeds to the egress output stage 1745. If the
egress interface is local, the packet is sent to the proper VLAN.
On the other hand, if the egress interface is remote, the SR
forwards the packet to the dummy interface's SR, which then sends
the packet out via the proper VLAN. In some embodiments, the packet
is sent to the correct peer SR, which then performs ARP and outputs
the packet. However, this technique requires either for the packet
to store next-hop information or for the peer SR to re-perform the
routing stage. In some embodiments, the egress output stage does
not decrement TTL. The TTL is instead decremented by either the
routing stage at this SR or, if received through redirect at the
output stage of a different SR, then by the routing stage at that
different SR.
IV. ECMP Routing in Multi-Tier Logical Networks
As mentioned above, some embodiments use equal-cost multi-path
routing techniques, for both northbound and southbound packets,
with regard to the SRs of a PLR. In some embodiments, the use of
ECMP is only allowed when no stateful service is configured on the
logical router that interfaces with the physical network (e.g., the
PLR in a two-tier topology). In order for packets to be forwarded
using ECMP techniques, a PLR requires multiple uplinks and for BGP
(or another dynamic routing protocol) to be enabled. In some
embodiments, the multiple uplinks may be located in the same L2
domain.
As described previously, the user (administrator) associates a
logical router with a particular set of physical gateway machines.
The management plane then assigns the various uplinks of the PLR to
different gateway machines in this set of physical gateway
machines. Some embodiments enforce a rule that the various gateway
machines within a specifiable set have uniform physical
connectivity to the external network (e.g., that all of the
machines have access to the same set of VLANs), which simplifies
the logic at the management plane. At each gateway machine to which
the management plane has assigned an uplink, an SR is created.
Some embodiments place additional requirements on the uniform
physical connectivity. Specifically, in some embodiments all of the
gateway machines spanned by a PLR have the same L3 connectivity
(i.e., all of these machines connect to the same set of physical
routers). Furthermore, with BGP enabled (a requirement for ECMP),
all of these physical next-hops (the physical routers) are required
to have the same physical connectivity. This means that all SRs for
a particular PLR will receive the same set of routes from their
physical next-hops, with the possibility of transient route
differences between SRs that disappear fairly quickly. With this
set of requirements, the dummy uplinks are not required, as packets
will not need to be redirected between uplinks (as all uplinks have
the same policies and same connectivity).
FIGS. 18 and 19 illustrate a single-tier logical network topology
1800 and the management plane view of that topology that meets the
above-stated requirements for the use of ECMP. The network topology
1800 is similar to that of FIG. 9, but each of the two uplinks has
the same L3 connectivity. The logical network topology 1800
includes two logical switches 1805 and 1810 that connect to a
logical router 1815. The configuration of these components is the
same as with the network topology 900, except for the configuration
of the physical routers to which the uplinks connect. That is, the
interfaces between the logical router 1815 and the logical switches
1805 and 1810 are all the same, and the two uplinks U1 and U2 of
the logical router 1815 connect to physical routers 1820 and 1825
with the same next hop IP addresses. However, whereas in the
previous example the physical routers provided connectivity to
different networks, here the physical routers both have the same L3
connectivity to the Internet.
Thus, in FIG. 19, the management plane view 1900 of the logical
network is nearly the same as well. The management plane again
defines, for the logical router 1815, a DR component 1905, two SRs
1910 and 1915 for the two uplinks, and a transit logical switch
1920. The only modification to the configuration is that no dummy
interfaces are configured on the SRs, because the two uplinks have
the same configuration and RIB, so one of the SRs should not
receive a packet that needs to be forwarded out of the second SR.
As such, the routes in the RIB for redirection that were described
in the previous section will not be included in the RIB of these
SRs.
In some embodiments, ECMP is used in conjunction with BGP (or other
dynamic routing protocols). Each SR of the logical router
establishes a BGP session with the one or more physical routers to
which it connects. For instance, in the example of FIG. 18 and FIG.
19, the SR 1910 initiates a session with the physical router 1820,
while the SR 1915 initiates a session with the physical router
1825. In some embodiments, each of the uplinks would be connected
to both of the physical routers, and thus each uplink would have
two routing sessions. In some embodiments, a module on the gateway
machine separate from the SR implementation initiates the BGP
session with the router. For instance, when the SR is implemented
as a VM, the BGP module may be part of the VM or a separate module
operating as part of the hypervisor, in a separate VM or other data
compute node, etc. During these sessions, the SR advertises the
prefixes in the logical space (e.g., the logical switch subnets
1.1.1.0/24 and 1.1.2.0/24) to the physical routers, using the same
metric for each of the prefixes. The BGP integration techniques of
some embodiments are described in U.S. patent application Ser. No.
14/214,561, filed Mar. 14, 2014, now issued as U.S. Pat. No.
9,590,901, which is incorporated herein by reference.
With all of the SRs advertising the same routes to the physical
routers, the physical routers can then treat the SRs as equal-cost
routing options, and spread traffic through the various SRs. In the
example shown in FIGS. 18 and 19, each of the physical routers can
only send packets to one of the SRs. However, each of the physical
routers has the same connectivity, so packets sent from the
networks behind them towards the logical network will be spread
evenly between the two routers 1820 and 1825, and therefore spread
evenly between the two SRs. When each SR connects to all of the
physical routers, then each of these physical routers can spread
traffic evenly between the SRs on their own.
For northbound packets, the DR of some embodiments uses ECMP
techniques to distribute packets among the various SRs, which
provide equal connectivity for northbound packets. By running BGP
(or a different dynamic routing protocol), the SRs learn routes
from the physical routers in addition to advertising routes for the
logical network prefixes. As mentioned, the SRs locally incorporate
these routes into their RIBs, and can recalculate their FIBs based
on the newly learned routes. However, for the DR to use ECMP, the
routes must also be given to the RIB of the DR, which is
implemented at numerous machines.
In some embodiments, the SRs report the learned routes to the
centralized network controllers that configure and manage the SRs
(as well as the MFEs that implement the distributed logical
forwarding elements). The centralized controllers then update the
RIB of the DR accordingly, and distribute the updates to the MFEs
that implement the DR. Different embodiments may update the DRs at
different rates, depending on the desired balance between keeping
an up-to-date RIB and the processing load on the central
controllers. Rather than distributing the RIB, some embodiments
compute the FIB at the centralized controllers, then distribute the
updated FIB to the MFEs that implement the DR.
In other embodiments, rather than continuously updating the routes,
the centralized controller instead adds to the DR RIB default
routes that point to all of the SRs. These routes are classified as
management plane internal, so they are only used by the DR if they
are not overruled by static routes input by an administrator.
Because the routes for the different SRs have the same
administrative distance metric, the DR treats them as equal-cost
options, dividing traffic between the SRs with ECMP techniques.
V. Active-Standby for Stateful Services
While the above section describes the SR setup for active-active
configuration with ECMP (when all of the two or more SRs are
treated as equal options), some embodiments use an active-standby
configuration with two SRs. Some embodiments use the active-standby
configuration when stateful services are configured on the SRs. In
this case, the benefit of avoiding having to continuously share
state between the SRs may outweigh the negatives of sending all of
the northbound and southbound traffic between multiple SRs (while
using a standby for backup in case of failure). In the
active-standby case, the state is periodically synchronized between
the two SRs, though this need not be done at per packet speeds.
In some embodiments, for active-standby configuration, the
administrator is required to configure two uplinks when defining
the logical router, and the uplinks need not be in the same L2
domain. However, because the active and standby SRs should be
equivalent options to the DR (with the active SR the preferred of
the two options), some embodiments require the two SRs to have
uniform L3 connectivity. This is, of course, not an issue when the
active-standby SRs are configured for a TLR with stateful services,
as both SRs will have one next hop, the DR of the PLR to which the
TLR connects. For a PLR in active-standby configuration, the two
uplinks should be configured with the same connectivity in some
embodiments. In addition, for a PLR, some embodiments allow (or
require) the configuration of dynamic routing protocols (e.g., BGP)
on the SRs.
FIG. 20 illustrates a management plane view 2000 of the logical
network topology 1800 when the logical router is configured in
active-standby mode, rather than active-active (ECMP) mode. Here,
the only difference in configuration from the active-active mode
shown in FIG. 19 is that the southbound interfaces of the SRs 2010
and 2015 are assigned the same IP address, but different MAC
addresses.
The management plane configures the DR 2005 in the same manner as
in the general case of FIGS. 9 and 10, in terms of assigning MAC
and IP addresses to its southbound and northbound interfaces. When
constructing the RIB, the same connected routes are used, and the
same static route rules apply as described above in Section II
(e.g., northbound routes are copied to the DR but modified to set
the SR IP address as its next hop). In this case, because there is
only one IP address for the SR, all northbound routes use this
single IP as the next hop address. Similarly, rather than creating
multiple default routes to the various different SR IP addresses, a
single default route with this lone IP address as the next hop is
added to the RIB of the DR. Thus, the RIB for the DR 2005 in FIG.
20 includes the following routes: 1.1.1.0/24 output to L1
1.1.2.0/24 output to L2 192.168.100.0/24 output to DRP1
192.168.1.0/24 via IP1 192.168.2.0/24 via IP1 0.0.0.0/0 via IP1
Each of the SRs 2005 will be configured in mostly the same manner.
When the logical router is a PLR (or in a one-tier topology, as in
the example), the IP and MAC addresses of the northbound interfaces
are the same as those assigned to the two uplinks configured for
the PLR. On the other hand, when the logical router is a TLR, it
may only have one uplink that is configured to connect to the PLR.
In this case, the IP addresses of the two northbound interfaces are
the same, but each SR is assigned a different MAC address.
Similarly, in either of these two cases (PLR or TLR), a single IP
address is assigned to the two southbound interfaces (as in FIG.
20, in which both of these interfaces have an IP address of IP1),
with two different MAC addresses for the two SRs.
Any uplink-independent service policies the controller pushes to
both of the SRs identically, in some embodiments. If any service
policies that depend on the uplink are allowed and configured, then
these are pushed to the SRs on which the uplink with which they are
associated exists. In addition, any dynamic routing configurations
of a logical router port are transferred to the northbound
interface of the SRs.
The RIB for the SRs is similar to that described above in Section
II for the general case. Static and connected routes that egress
from an uplink of the logical router are added to the RIB of the SR
without modification. For each southbound interface of the logical
router (e.g., routes for logical switch subnets), a route for the
network is added with the next hop IP address set to the northbound
interface of the DR. Any route in the RIB of the logical router
that egresses from this southbound interface is also added to the
RIB of the SR with this same next hop IP address. The RIB of SR1
2010 in the example of FIG. 20 will include the following routes,
prior to learning any additional routes via dynamic routing
protocols: 0.0.0.0/0 output to U1 via 192.168.1.252 192.168.1.0/24
output to U1 192.168.100.0/24 output to SRP1 1.1.1.0/24 via IP3
1.1.2.0/24 via IP3
In addition, when the SR is set as a standby SR (rather than active
SR), the SR does not answer ARP on its southbound interface in some
embodiments. ARP packets for the southbound IP of the SR will be
broadcast on the transit logical switch that connects the SRs and
the DR, and both the active and standby SRs will be responsive to
that IP address. However, only the active SR will respond to ARP
requests, so that the DR will route packets to the MAC address of
the active SR rather than the standby SR. The standby SR in some
embodiments will nevertheless accept packets received by the
northbound interface, in order to run its dynamic routing protocol
and keep an up-to-date set of routes in case it becomes the active
SR. However, the standby SR does not advertise prefixes to the
external networks, unless it becomes active.
VI. SR Failover
As described above, the SRs may be implemented in different
embodiments as VMs or other data compute nodes or as VRFs within
DPDK-based datapaths. In both cases, the possibility of different
types of failure (partial tunnel failure, complete tunnel failure,
physical machine crashes, etc.) may cause a SR to go down. However,
different SR implementations may respond to different types of
failures in different manners.
A. Failure Handling with DPDK-Based SRs
In some embodiments, as described, the SRs of a logical router
operate on gateway machines, or edge nodes, as VRFs within the
DPDK-based datapaths. These gateway machines are grouped into sets
(e.g., based on physical location within a datacenter), and the
gateway machines of a set that collectively host all of the SRs for
a particular logical router are connected by a set of tunnels
(e.g., a full mesh of tunnels in some embodiments). Thus, tunnels
exist between all of the gateway machines on which a SR
operates.
Some embodiments use Bidirectional Forwarding Detection (BFD)
sessions to maintain these tunnels, in order to monitor the
aliveness of peer gateway machines. However, as using only the
single BFD session between the tunnel endpoints would require
depending on a single information channel to detect the aliveness
of a peer, some embodiments also use a second channel between each
pair of gateway machines. Specifically, in some embodiments, a
separate management network exists between the gateways for sending
control data (e.g., for communication with the network
controllers). Thus, each gateway has a separate IP address on the
management network, and these connections may be used to send
heartbeat messages over the management network. This prevents the
possibility of tunnel failure between two peers resulting in both
of the gateway machines determining that the other has crashed and
initiating actions that cause confusion when the peer is not
actually down. Instead, during tunnel failure, each of the nodes
can detect that their peer machine is still up, and thus conclude
that the tunnel has failed and not the peer machine (and thus its
SRs) itself.
In some embodiments, the failure conditions are different for SRs
of PLRs and SRs of TLRs. When the tunnels of a gateway machine that
provide connectivity to the MFEs on which the user VMs run (e.g.,
the MFEs 1325 of FIG. 13 to which the user VMs directly connect)
fail, all SRs on the gateway machine are no longer operational
(even for the SRs of PLRs, as traffic sent to the PLRs by external
physical routers will be blackholed. On the other hand, when a
gateway machine loses its connectivity to the physical routers, the
SRs of TLRs on the gateway are still treated as operational, as
northbound traffic to the TLRs will have the DR of a PLR as a next
hop, which should always be available (as it is also implemented
within the datapath on the gateway). The SRs of PLRs, however, are
no longer considered operational, as any northbound traffic
originating from VMs of the logical network will be blackholed.
When a gateway machine that hosts SRs of PLRs loses its physical
connectivity (or its BGP sessions), in some embodiments the gateway
machine sends a message (e.g., a specific diagnostic code such as
"concatenated path down") to other gateway machines that host SRs
of the same PLR.
Based on the BFD session on the tunnel with a peer, the status of
heartbeat messages over the second (e.g., management) channel with
the peer, and whether a message has been received from the peer
indicating that the peer's physical connectivity is down, a first
gateway machine can make a conclusion about its peer second gateway
machine and take certain actions based on those conclusions. For
example, if the tunnel is active and no connectivity down message
is received, then the first gateway machine concludes that the peer
second gateway machine is healthy, and continues processing packets
as normal. However, if the tunnel to the peer is up, but the
connectivity down message has been received, then the first gateway
machine concludes that the peer is still active but has lost its
physical connectivity. As such, the SR on the first gateway machine
takes over the SR (as described below) on the second gateway
machine if the SR belongs to a PLR, but takes no action with regard
to SRs of TLRs.
If the tunnel goes down (based on the BFD session no longer being
active) between the first gateway machine and the peer second
gateway machine, but the secondary channel heartbeat messages are
still received, then the first gateway machine concludes that the
peer second gateway machine is still healthy and handling
northbound and southbound packets (although redirection may be a
problem if needed). However, if both the tunnel and the secondary
channel are down, then the first gateway machine concludes that the
peer has gone down (e.g., crashed). In this case, the SR on the
first gateway machine takes over for the SR on the second gateway
machine (as described below), irrespective of whether the SRs
belong to a PLR or a TLR.
In some embodiments, each gateway machine has a local network
controller (sometimes referred to as a chassis controller) that
operates on the machine. The chassis controller of some embodiments
receives data tuples from the central network controller and uses
the data tuples to configure the MFE on the machine. This chassis
controller is also, in some embodiments, responsible for
determining when the health status of its gateway machine changes,
as well as when that of a peer gateway machine changes. When one of
the three indicators of communication (tunnel BFD session,
secondary channel, and physical connectivity down messages) between
the gateway machines is affected (based on a loss of connectivity,
the gateway machine crashing, etc.), the chassis controller of some
embodiments determines how this affects each SR hosted on its
gateway machine.
The actions taken by the chassis controller with respect to a
particular one of its SRs then depend on (i) whether the SR belongs
to a PLR or a TLR, (ii) whether the SR works in active-active or
active-standby mode, (iii) its own local health status, and (iv)
the health status of the peer gateway machine(s) hosting the other
SRs of the same logical router. For example, the chassis controller
could determine that its local SR should no longer be treated as
functional, in which case it may send signals to this effect to a
combination of (i) other gateway machines, (ii) the host machines
on which user VMs reside, and (iii) physical external routers. The
chassis controller can also make the determination that a local SR
should become active, in which case it may start a failover process
to activate the SR. Furthermore, the chassis controller could make
the determination that a remote SR is no longer functional, and
start a failover procedure to take over this remote SR locally.
When a failure condition is detected, various embodiments may take
various different actions to partially or completely remedy the
situation. Different types of failure cases may include complete or
partial tunnel failure, gateway machine or MFE crashes, link
aggregate group (LAG) status going down, BGP session failing,
non-uniform routes among SRs. While resurrection of an SR is not
actually a failure scenario, it also results in actions taken by
the gateway machine chassis controller(s) to manage the SRs.
1. Complete Tunnel Failure
Complete tunnel failure may occur due to the gateway machine
crashing, or due to pNIC or physical network issues. When complete
tunnel failure occurs at a particular gateway machine, (i) all of
the MFEs at host machines with user VMs or other data compute nodes
lose tunnels to the particular gateway machine, (ii) other gateway
machines lose tunnels to the particular gateway machine, and (iii)
the particular gateway machine loses tunnels to the other gateway
machines.
From the point of view of the MFE at a host machine, when its
tunnel to the particular gateway machine fails, the DR of a PLR can
reach some SRs (assuming all of the gateway machines spanned by the
PLR do not fail at once) but cannot reach the SR on the particular
gateway machine. As such, in some embodiments, the datapath or
chassis controller on the host machine automatically removes the
affected routes (that use the SR on the particular gateway machine
as the next hop IP address) from the FIB of the DR. Some
embodiments associate each next hop with a virtual tunnel endpoint
(VTEP) of the respective gateway machine. When the tunnel towards a
particular VTEP is down, all next hops associated with the
particular VTEP are marked as down, and thus removed when
calculating the FIB for the DR by the local chassis controller.
The other gateway machines detect the failure of the particular
gateway machine tunnels through the status of the BFD sessions, and
that the secondary channel is still up. These other gateway
machines (e.g., the local chassis controller on the other gateway
machines) can then initiate a failover process to take over the SRs
hosted on the failed gateway machine.
For SRs on the failed gateway machine that are configured in
active-active mode, some embodiments use a ranking mechanism to
determine how the failed SR is taken over by one of the other
machines. In some embodiments, the management plane assigns each of
the N SRs in an active-active configuration a ranking, from 1 to N.
These rankings may be assigned randomly, or using a different
technique, and are distributed to the local chassis controller of
all of the gateway machines that host SRs for a particular logical
router in active-active configuration. Based on the ranking of the
failed SR, the next-highest ranked SR automatically takes over the
southbound interface of the failed SR. For the northbound
interface, no action needs to be taken by the other SRs, as the
physical routers will recognize that the SR is down when the BGP
session terminates. To take over the interface, the overtaking SR
sends several gratuitous ARP (GARP) messages for all of the IP
addresses that it is taking over to the transit logical switch on
its southbound interface. These messages announce that the IP
addresses are now associated with the MAC address of its southbound
interface. If the failed SR has already taken over other IP
addresses (due to previous failure of other SRs for the logical
router), then multiple IP addresses are taken over by the new
overtaking SR.
For SRs on the failed gateway machine that are configured in
active-standby mode, some embodiments treat the failure of the
active SR and the failure of the standby SR differently.
Specifically, if the failed SR is a standby, some embodiments take
no action (i.e., they do not instantiate a new standby machine), on
the assumption that the standby machine will be brought back up in
good time. If the failed SR is the active SR of a TLR, then both
the southbound and northbound interface IP addresses are migrated
to the standby SR. Because the TLR has only a single uplink, both
of the SRs share both northbound and southbound IP addresses, but
with different MAC addresses. In both cases, some embodiments send
GARP messages to the relevant transit logical switch to effectuate
the migration of the IP addresses. For the SR of a PLR, only the
southbound interface is migrated, because the two uplinks should
have separate IP addresses even in active-standby mode.
Furthermore, the new active SR begins advertising prefixes to
physical routers to draw southbound packets to itself rather than
to the failed SR. In the case in which the same IP and MAC
addresses are used for the southbound interfaces of the
active-standby SRs, some embodiments use Reverse ARP (RARP) to
refresh the MAC:VTEP mapping (that is, so packets will be sent over
the correct tunnel to the newly active SR).
On the gateway machine that has lost all of its tunnels, the
chassis controller determines that the most likely cause is some
sort of local failure, and thus determines that its local SRs
should no longer be active. Thus, any SR that is announcing
prefixes to the external physical routers via BGP session withdraws
its announced prefixes, so as to avoid attracting southbound
traffic that will be blackholed.
2. Partial Tunnel Failure
Partial tunnel failure occurs when only some of the tunnels between
the gateway machine and other machines in the datacenter go down.
This could be due to complete failure at one of the machines with a
tunnel to the particular gateway machine (which would result in the
loss of one tunnel), due to conditions at the particular gateway
machine that result in some of its tunnels going down, etc.
Described here is the case when conditions at the particular
gateway machine result in a subset of its tunnels failing. As a
result, (i) some of the MFEs at host machines with user VMs or
other data compute nodes lose tunnels to the particular gateway
machine, (ii) some of the other gateway machines lose tunnels to
the particular gateway machine, and (iii) the particular gateway
machine loses tunnels to some other gateway machines.
The MFEs at host machines that lose tunnels to the particular
gateway machine treat this in the same manner as complete tunnel
failure, as from the perspective of the host machine this is simply
an unreachable gateway. As such, the datapath or chassis controller
on the host machine automatically removes the affected routes that
use the SR on the particular gateway machine as the next hop IP
address from the FIB of the DR, as described above in subsection
1.
As noted, partial tunnel failure can result in various different
scenarios. For instance, in some cases, a gateway machine may be
reachable by some of the host machine MFEs, but not by its peers.
Referring to FIG. 13 (which illustrates SRs as VMs but is
nevertheless applicable) as an example, the gateway machine 1330
might be reachable by the host machines 1305-1320 but not reachable
by gateways 1335 and 1340. In this case, the local chassis
controller on the gateway machine 1330 will take over the SRs of
the PLR that are running on both gateway machines 1335 and 1340. In
addition, the gateway machine 1335 (or machine 1340, depending on
the ranking) will take over the SR running on the gateway machine
1330. This results in some of the MFEs (that can reach all of the
gateway machines) receiving replies from multiple gateway machines
when the DR running on it sends an ARP request for the southbound
interface IP address of the SR hosted on the first gateway machine
1330. So long as the SRs are in an active-active configuration
(with no stateful services), this will not create a correctness
problem. However, in the case of an active-standby configuration,
this would mean that both of the SRs are now active, which could
cause traffic disruption issues.
Partial tunnel failure can also cause problems in active-standby
mode when, at a particular gateway machine, the tunnels to some of
the host machines go down, but the peer gateway machines remain
reachable. In this case, because the tunnels between the SRs are
functioning, no failover occurs. In active-active mode, the
datapath at the host machines (or the local chassis controller) can
make the decision to forward traffic over the tunnels that are
still up without issue. However, in active-standby mode, if the
tunnels to the active SR are down, then the MFE will send packets
to the standby SR, which does not process them. Similarly, in both
active-active and active-standby configurations, the gateway
machine may not be able to pass on southbound traffic from physical
routers, which is therefore blackholed in some embodiments.
3. Machine Crash
In some cases, the entire gateway machine may crash, or the DPDK
fastpath may crash. As the fastpath is responsible for sending the
BFD packets in some embodiments, either of these situations is the
same as a complete tunnel failure. As the MSR process (which
handles BGP sessions for the SRs on the gateway machine) may
continue to run when only the fastpath crashes (and not the entire
gateway machine), physical routers will still have the ability to
send packets to the gateway machine. This traffic is blackholed in
some embodiments until the fastpath is restarted.
4. LAG Status Down
In some embodiments, the gateway machines use link aggregate groups
(LAG) to reach the external physical routers. When a gateway
machine that hosts a SR of a PLR loses the entire LAG, in some
embodiments the machine sends the physical connectivity down
message (described above) over tunnels to its peer gateway machines
that also host the SRs of that PLR. In this case, the takeover
procedure described above with respect to complete tunnel failure
occurs (the next highest-ranked SR takes over the IP addresses of
the SR).
Some embodiments instead mark all tunnels as down as a technique to
induce failover. However, this results in the SRs of TLRs on the
machine being failed over to other gateway machines as well, which
is unnecessary when only the physical connectivity is down. This
can lead to numerous GARP messages sent to the MFEs at host
machines, and therefore some embodiments use the first technique
that only fails over the SRs of PLRs.
In some cases, only some of the physical uplinks in the LAG go
down. So long as at least one of the physical uplinks in the LAG
remains functional, the gateway machine does not take any action
and continues operating as normal. Furthermore, in some
embodiments, tunnel traffic (within the datacenter) uses a separate
LAG. If that entire LAG goes down, this results in complete tunnel
failure, described above in subsection 1.
5. BGP Session Down
In some cases, the BGP session for the SRs may go down (e.g.,
because the MSR process on the gateway machine crashes). When
graceful restart is enabled for the BGP process, no failover
actions need to be taken so long as the session is reestablished
within the timeout set for graceful restart. In order to be able to
detect when the MSR process (or other BGP module) has gone down,
some embodiments require the process to refresh the status of all
BGP sessions periodically, even if the status has not changed.
On the other hand, if graceful restart is not enabled or the
timeout for the restart expires, the gateway machine of some
embodiments sends a physical connectivity down message to its peer
gateway machines that also host SRs for the same PLR, in order to
indicate that its SR is no longer functioning. From the perspective
of the peer gateway machines, this is the same as if the LAG status
is down, in that the SR interfaces on the gateway with the
non-functioning BGP session will be taken over by the next-highest
ranked SR. In addition, so long as one BGP session is functioning,
and all physical next hops have the same L3 connectivity, then no
failover action need be taken.
6. Non-Uniform Routes Among SRs
Failures in the external physical network to which the SRs of a PLR
connect may also affect the SRs. For instance, some external
physical routers might withdraw a route for a subnet, while other
physical routers do not. Some embodiments solve this issue locally
on the gateway machines without involving the central network
controllers.
As mentioned, in some embodiments, the SRs have iBGP peering with
each other, and eBGP routes (learned from the external physical
routers) are sent over the iBGP sessions without changing the next
hop. By reference to FIG. 10, any eBGP routes learned by the SR
1015, which have a next hop of 192.168.2.252 (in the same subnet as
the uplink U2), are learned by the SR 1010 via iBGP. These routes
are then installed in the SR 1010 with a next hop of 192.168.2.252
because the SR has a dummy interface (U2') for the actual uplink on
the other SR 1015. This same technique also happens for route
withdrawal scenarios.
7. SR Resurrection
Although SRs may go down for various reasons indicated in the
previous subsections, the SRs will generally be brought back up
after a period of time. This may be indicated at other machines by
a BFD session towards the particular gateway machine with the SR
that had failed coming back up, or by the receipt of a message
clearing the physical connectivity down flag. In some embodiments,
the local chassis controller on all of the other gateway machines
then evaluates whether the local SRs should continue taking over
the remote SRs using the same methodology as described above.
For example, if an IP address currently taken over by a local SR
from a remote SR should be given back to the remote SR (i.e., the
local SR should no longer be taking over the IP address), then the
local SR stops answering ARPs for the IP address. For some
embodiments, the local chassis controller removes the IP address
from the local SR's southbound interface. If an IP address should
be taken over by a local SR (e.g., because it has come back up),
then it follows the failover procedure described above in
subsection 1. In addition, if a local SR is designated as standby,
and the active SR resumes functioning, then the local SR stops
advertising prefixes to the external physical routers. Similarly,
if a local SR designated as active resumes functioning, it also
resumes advertising prefixes.
B. Failure Handling with VM-based SRs
As noted above, some embodiments use VM (or other data compute
nodes) on the gateway machines to host SRs in a datacenter, rather
than (or in addition to) hosting SRs in DPDK-based datapaths of the
gateway machines. FIG. 21 illustrates an example physical
implementation 2100 of three gateway machines 2105-2115 that host
the three SRs 2120-2130 for a particular PLR. Each of the gateway
machines includes a MFE, a BGP process (e.g., the MSR process
described in the above subsection A), and a local control plane, or
chassis controller.
The MFEs 2135-2145 on the gateway machines 2105-2115 may be virtual
switches such as OVS, ESX, a different hypervisor-based virtual
switch, or other software forwarding elements that can handle
distributed L2 and L3 forwarding. As shown, the three MFEs
2135-2145 have a full mesh of tunnels between them, and these three
MFEs also have tunnels to MFEs located at a set of host machines
2150-2155, that host user VMs. The host machines 2150-2155 also
have local control planes.
The physical implementation 2100 of a network topology with three
active SRs operating as VMs will be used in this subsection to
describe various different failure scenarios. In general, when one
of the VMs hosting an SR fails or the tunnels between them fail,
the other peer SRs will attempt to take over the failed SR's
responsibilities. In some embodiments, the SRs that belong to the
same logical router send heartbeat messages to each other via the
transit logical switch periodically (e.g., by broadcasting a
heartbeat message onto the transit logical switch, which will be
delivered to all of the other SRs on the transit logical
switch).
1. Crash of VM Hosting an SR
In some cases, the actual VM that hosts one of the SRs may crash
due to any number of reasons. As mentioned above, when the SRs
operate in active-active mode (as in FIG. 21), then the management
plane assigns each of the VMs a rank for use in failover scenarios.
In the case of FIG. 21, SR1 on gateway machine 2105 is the highest
ranked, SR2 on gateway machine 2110 is the second-highest ranked,
and SR3 on gateway machine 2115 is the third-highest ranked among
the SRs.
FIG. 22 conceptually illustrates the result of one of the VMs
crashing. Specifically, this figure illustrates that the VM in
which the SR 2125 operates on the gateway machine 2110 crashes. As
a result, this VM is unable to send out heartbeat messages to the
other SRs 2120 and 2130, although the tunnels between the gateway
machines are still operational (e.g., for other SRs that operate in
other VMs on the gateway machine. In this sense, while the various
failure mechanisms affect all of the DPDK-based SRs on a machine
(as they are all implemented as VRFs within a datapath), crashes of
the VMs for the VM-based SRs only affect the single SR operating in
that VM, and not the other SRs on the gateway machine.
The other SRs 2120 and 2130 detect the failure of the SR 2125 due
to the missing heartbeats, and therefore take over responsibility
for the failed SR. Normally, all of the SRs store information for
the IP addresses of their own southbound interfaces as well as the
southbound interfaces of the other SRs. That is, SR 2120 stores
information about its own interface to the transit logical switch
that connects the SRs, as well as the corresponding interface of
the SRs 2125 and 2130. The SR 2120, however, normally only answers
ARP requests for its own interface.
When a SR's VM crashes, as shown in FIG. 22, the next highest
ranked SR that is still alive is responsible for taking over the
failed SRs southbound interface IP address, as well as any IP
addresses the failed SR had previously taken over. For instance, if
SR3 2130 had previously crashed, then its southbound interface
would be taken over by SR2 2125. Thus, FIG. 22 illustrates that the
SR 2120 is now acting as both SR1 and SR2. Assuming the logical
network forwards northbound packets using ECMP principles, the host
machines 2150-2155 should route two-thirds of all northbound
traffic for the logical router to which the SRs 2120-2130 belong to
the VM on gateway 2105 (e.g., to that VM's MAC address), as packets
forwarded to the IP addresses of both SR1 and SR2 will be routed to
that MAC.
In order for the VM on the gateway 2105 to take over the IP address
of SR2 2125, the VM sends GARP messages for this IP address (and,
in other cases, all IP addresses that it takes over) to the transit
logical switch that connects the DR and the SRs 2120-2130. In some
embodiments, the VM sends multiple GARP messages in order to better
ensure that the message is received. The MFE 2135 receives these
GARP messages, and sends them to the MFE 2145 (for delivery to SR3
2130) as well as to the MFEs at the various hosts 2150-2155 (so
that the DR will know to remove from its ARP cache the old SR2 IP
to MAC address mapping).
In the case of two SRs in active-standby mode (e.g., if the SRs
belong to a TLR, or a PLR with stateful services configured), then
the southbound interfaces share the same IP address but with
different MAC addresses in some embodiments, as described above. If
the standby VM crashes, then in some embodiments the management
plane does not initiate a new standby, on the assumption that the
VM will come back up without the active SR's VM also failing. When
the active SR's VM fails, however, the standby VM identifies this
failure (as no heartbeat messages are received), and generates GARP
messages so as to remove the mapping of the southbound IP address
to the crashed SR's MAC address in the ARP table for the DR in the
host machine MFEs (so that these MFEs will route packets to the new
active SR rather than the old active SR). In some embodiments, the
tunneling protocol layer (e.g., the VXLAN layer) on the host
machines also learns the MAC:VTEP mapping for the new MAC address.
the same IP and MAC addresses are used for the southbound
interfaces of the active-standby SRs, some embodiments use Reverse
ARP (RARP) to refresh the MAC:VTEP mapping at the host machine MFEs
(so packets will be sent over the correct tunnel to the newly
active SR).
Lastly, if the standby (now active) VM operates as a SR for a PLR,
it begins route advertisement to the physical external routers.
When the BGP process on the gateway machine with the failed SR
operates outside of the VM with the SR, then in some embodiments
the local control plane at that gateway machine stops the BGP
process from continuing to advertise routes as well, so that the
gateway machine will not attract ingress traffic for the failed
SR.
2. Complete Tunnel Failure
Complete tunnel failure may occur due to the gateway machine
crashing, the MFE on the gateway machine having problems, or due to
pNIC or physical network issues. When complete tunnel failure
occurs at a particular gateway machine, (i) all of the MFEs at host
machines with user VMs or gateway machines lose tunnels to the
particular gateway machine, (ii) SRs on other gateway machines
determine that the SRs on the particular gateway machine have
failed, and (iii) the SRs on the particular gateway machine
determine that the SRs on the other gateway machines have failed.
In some embodiments, if the particular gateway machine no longer
receives heartbeat messages on any of the tunnels, the logic on the
particular gateway machine determines that it has lost its tunnel
connectivity, not that the other VMs have done so.
FIG. 23 conceptually illustrates the result of complete tunnel
failure at the MFE 2145 on the gateway machine 2115 that hosts SR3
2130. As shown, the MFE 2145 has failed such that the tunnels from
this MFE to the other gateway machines and host machines are down
(indicated by the dotted lines). As a result, the other SRs that
belong to the same PLR (configured in active-active mode) start a
failover process to take over the southbound interface IP addresses
of the failed SR 2130.
In some embodiments, the next-highest ranked SR that is still alive
is responsible for taking over the failed SR's southbound interface
IP address, as well as any IP addresses the failed SR had
previously taken over. Thus, FIG. 23 illustrates that the VM for SR
2125 is now acting as both SR2 and SR3. Assuming the logical
network forwards northbound packets using ECMP principles, the host
machines 2150-2155 should route two-thirds of all northbound
traffic for the logical router to which the SRs 2120-2130 belong to
the VM on gateway 2110 (e.g., to that VMs MAC address), as packets
forwarded to the IP address of both SR2 and SR3 will be routed to
that MAC.
In order for the VM on the gateway 2110 to take over the IP address
of SR3 2130, the VM sends GARP messages for this IP address (and,
in other cases, all IP addresses that it takes over) to the transit
logical switch that connects the DR and the SR 2120-2130. In some
embodiments, the VM sends multiple GARP messages in order to better
ensure that the message is received. The MFE 2140 receives these
GARP messages, and sends them to the MFE 2135 (for delivery to SR1
2120) as well as to the MFEs at the various hosts 2150-2155 (so
that the DR will know to remove from its ARP cache the old SR2 IP
to MAC address mapping).
In the case of two SRs in active-standby mode (e.g., if the SRs
belong to a TLR, or a PLR with stateful services configured), then
the southbound interfaces share the same IP address but with
different MAC addresses in some embodiments. If the tunnels from a
gateway machine with a standby SR fail, then the management plane
does not initiate a new standby SR in some embodiments. When the
tunnels from a gateway machine with an active SR fail, however, the
standby VM identifies this failure (as no heartbeat messages are
received from the active SR), and generates GARP messages so as to
remove the mapping of the southbound IP address to the failed SR's
MAC address in the ARP table for the DR in the host machine MFEs
(so that these MFEs will route packets to the new active SR rather
than the old active SR). In some embodiments, the tunneling
protocol layer (e.g., the VXLAN layer) on the host machines also
learns the MAC:VTEP mapping for the new MAC address. Lastly, if the
standby (now active) VM operates as a SR for a PLR, it begins route
advertisement to the physical external routers. In addition, in
some embodiments, the gateway machine with the failed tunnels stops
its own BGP process from continuing to advertise routes.
3. Partial Tunnel Failure
Partial tunnel failure occurs when only some of the tunnels between
the gateway machine and other machines in the datacenter go down.
This could be due to complete failure at one of the machines with a
tunnel to the particular gateway machine (which would result in the
loss of one tunnel), due to conditions at the particular gateway
machine that result in some of its tunnels going down, etc.
Described here is the case when conditions at the particular
gateway machine result in a subset of its tunnels failing. As a
result, (i) some of the MFEs at host machines with user VMs lose
tunnels to the particular gateway machine, (ii) some of the other
gateway machines lose tunnels to the particular gateway machine,
and (iii) the particular gateway machine loses tunnels to some
other gateway machines.
The MFEs at host machines that lose tunnels to the particular
gateway machine treat this in the same manner as complete tunnel
failure, as from the perspective of the host machine this is simply
an unreachable gateway. As such, the datapath or chassis controller
on the host machine automatically removes the affected routes that
use the SR on the particular gateway machine as the next hop IP
address from the FIB of the DR.
As noted, partial tunnel failure can result in various different
scenarios. For instance, in some cases, a gateway machine may be
reachable by some of the host machine MFEs, but not by its own
peers. Referring to FIG. 13 as an example, the gateway machine 1330
might be reachable by the host machines 1305-1320 but not reachable
by gateways 1335 and 1340. In this case, the local chassis
controller on the gateway machine 1330 will take over the SRs of
the PLR that are running on both gateway machines 1335 and 1340. In
addition, the gateway machine 1335 (or machine 1340, depending on
the ranking) will take over the SR running on the gateway machine
1330. This results in some of the MFEs (that can reach all of the
gateway machines) receiving replies from multiple gateway machines
when the DR running on it sends an ARP request for the southbound
interface IP address of the SR hosted on the first gateway machine
1330. So long as the SRs are in an active-active configuration
(with no stateful services), this will not create a correctness
problem. However, in the case of an active-standby configuration,
this would mean that both of the SRs are now active, which could
cause traffic disruption issues.
Partial tunnel failure can also cause problems in active-standby
mode when, at a particular gateway machine, the tunnels to some of
the host machines go down, but the peer gateway machines remain
reachable. In this case, because the tunnels between the SRs are
functioning, no failover occurs. In active-active mode, the
datapath at the host machines (or the local chassis controller) can
make the decision to forward traffic over the tunnels that are
still up without issue. However, in active-standby mode, if the
tunnels to the active SR are down, then the MFE will send packets
to the standby SR, which does not process them. Similarly, in both
active-active and active-standby configurations, the gateway
machine may not be able to pass on southbound traffic from physical
routers, which is therefore blackholed in some embodiments.
4. vNIC to Physical Router is Down
In some embodiments, each VM on which the SR runs uses a first vNIC
to connect to the MFE for packets sent to and from the physical
router(s) (if the SR belongs to a PLR), a second vNIC for sending
heartbeat messages to its peers, and a third vNIC for packets sent
to and received from the logical network. In some embodiments, some
or all of these vNICs may be the same. For instance, the SR might
use the same vNIC to send heartbeat messages and communicate with
physical routers, or to send heartbeat messages and communicate
with the logical network.
If the VM loses the first vNIC (with the physical router) for any
reason, in some embodiments the SR stops sending a heartbeat
message. As such, once its peer VMs that host the other SRs for the
PLR detect that the heartbeat messages have stopped from the SR,
they take failover actions as described above in subsection 1, as
if the VM had crashed. If the VM loses the second vNIC (for
heartbeat messages), the peer VMs will detect that no heartbeat
messages are incoming, and take the same failover actions to take
control of the failed SR's IP addresses. Lastly, if the VM loses
the third vNIC (for logical network traffic), it indicates the
situation in a heartbeat message, and the peers can follow the same
failover procedure.
5. BGP Session Down
In some cases, the BGP session for the SRs may go down (e.g.,
because the MSR process on the gateway machine crashes). When
graceful restart is enabled for the BGP process, no failover
actions need to be taken so long as the session is reestablished
within the timeout set for graceful restart. In order to be able to
detect when the MSR process (or other BGP module) has gone down,
some embodiments require the process to refresh the status of all
BGP sessions periodically, even if the status has not changed.
On the other hand, if graceful restart is not enabled or the
timeout for the restart expires, the gateway machine uses the
heartbeat message to indicate that the SR is no longer functioning
(e.g., by ceasing the heartbeat messages). From the perspective of
the peer SRs, the SR with non-functioning BGP will be treated as
down and the above failover procedures apply.
C. Failover Process
FIG. 24 conceptually illustrates a process 2400 performed by a SR
in case of failover of a peer SR. In various embodiments, this
process may be performed by either the local control plane
operating on the gateway machine of the SR (for either a VM or a
VRF in a DPDK-based datapath), the SR itself (if implemented as an
edge VM), or the datapath (if implemented as a VRF in a DPDK-based
datapath). That is, the operations of process 2400 apply to both of
the described types of SRs, though the implementation of the
processes may be different for the different types.
As shown, the process 2400 begins by determining (at 2405) that a
peer SR has failed. As described in the preceding subsections, a SR
might fail for various reasons, and in different capacities. For
example, the tunnel connectivity within the datacenter that enable
logical network communication might go down, the ability of the SR
to communicate with the external physical network could become
unavailable, the VM that implements the SR could crash (if the SR
is implemented as such), the datapath could crash, the entire
gateway machine hosting the SR could crash, etc. It should be
understood that in some cases (e.g., all tunnel connectivity from
the gateway machine going down, the datapath crashing, etc.) all of
the SRs on a gateway machine will be considered failed, and their
various peers will perform the process 2400 or a similar
process.
Upon determining that its peer SR has failed, the process 2400 then
determines (at 2410) whether to take over for the failed peer. For
example, if the failed peer is the standby SR in an active-standby
configuration, then the active SR needs not take any action. In
addition, for an active-active configuration, only one of the peer
SRs will need to take over for a failed SR. As described above,
which of the SRs takes over for a particular failed SR is
predetermined based on the ranks assigned by the management plane
at the time of creation of the SRs.
When the SR is not responsible for taking over for the failed SR,
the process ends. Otherwise, the process identifies (at 2415) the
southbound IP addresses owned by the failed peer, for which it is
now responsible. These may be different situations in active-active
compared to active-standby mode. Specifically, in active-standby
mode, the two SRs share an IP address on the southbound interface,
so the SR will simply take over acting on its own IP address. In
active-active mode, the SRs all have different southbound IP
addresses. In this case, the overtaking SR is now responsible for
the originally-assigned IP address of the failed SR, as well as any
additional southbound interface IP addresses that the failed SR had
previously taken responsibility for (due to failure of the other
peer SRs).
For each identified southbound IP address, the process 2400 sends
(at 2420) one or more GARP reply messages to the transit logical
switch that connects the SRs and the DR of their logical router.
The GARP messages identify the SR's own southbound MAC address as
now associated with the southbound IP address or addresses
identified at operation 2415. This enables the other components on
the transit logical switch to clear their ARP caches so as to avoid
sending packets routed to the identified IP address to the failed
destination. For the DR, implemented on numerous gateway and host
machines throughout the datacenter, the GARP reply is broadcast to
these numerous machines so that the ARP caches on the various MFEs
can be cleared.
The process then determines (at 2425) whether the SR performing the
process (or the SR on the machine whose local controller chassis is
performing the process) was previously a standby SR of a TLR. It
should be understood that the process 2400 is merely conceptual,
and that operation 2425 is implemented in some embodiments by
default on all TLR standby SRs, and that no specific determination
need be made. When the failed SR was the active SR in an
active-standby configuration, the standby SR is responsible for
attracting southbound traffic that previously would have been sent
to the failed SR.
Thus, if the SR was formerly a standby SR of a TLR, the process
2400 identifies (at 2430) the northbound IP address of the failed
peer, which it shares (as the TLR only is allowed one uplink in
some embodiments). The process next sends (at 2430) one or more
GARP reply messages to the transit logical switch that connects the
SRs to the DR of a PLR. The GARP messages identify the SR's own
northbound MAC address as now associated with the IP address of the
uplink configured for the TLR. This enables the DR of the PLR to
clear its ARP cache (more specifically, for the various MFEs that
implement this DR across the datacenter to clear their ARP caches).
The process then ends.
If the SR performing the process was not a standby SR of a TLR, the
process determines (at 2440) whether this SR was previously a
standby SR of a PLR. Again, it should be understood that in some
embodiments no specific determination is actually made by the SR or
local controller chassis that performs the process 2400. When this
SR was a standby SR for a PLR, the SR begins advertising (at 2445)
prefixes to its external physical routers. In the active-active
case, the SR would have already been advertising these prefixes in
order to attract ECMP traffic. However, in the active-standby
configuration, the standby does not advertise prefixes, instead
only receiving routes from the external routers. However, in order
to attract southbound traffic, the new active (formerly standby) SR
begins advertising prefixes. The process then ends.
VII. Electronic System
Many of the above-described features and applications are
implemented as software processes that are specified as a set of
instructions recorded on a computer readable storage medium (also
referred to as computer readable medium). When these instructions
are executed by one or more processing unit(s) (e.g., one or more
processors, cores of processors, or other processing units), they
cause the processing unit(s) to perform the actions indicated in
the instructions. Examples of computer readable media include, but
are not limited to, CD-ROMs, flash drives, RAM chips, hard drives,
EPROMs, etc. The computer readable media does not include carrier
waves and electronic signals passing wirelessly or over wired
connections.
In this specification, the term "software" is meant to include
firmware residing in read-only memory or applications stored in
magnetic storage, which can be read into memory for processing by a
processor. Also, in some embodiments, multiple software inventions
can be implemented as sub-parts of a larger program while remaining
distinct software inventions. In some embodiments, multiple
software inventions can also be implemented as separate programs.
Finally, any combination of separate programs that together
implement a software invention described here is within the scope
of the invention. In some embodiments, the software programs, when
installed to operate on one or more electronic systems, define one
or more specific machine implementations that execute and perform
the operations of the software programs.
FIG. 25 conceptually illustrates an electronic system 2500 with
which some embodiments of the invention are implemented. The
electronic system 2500 can be used to execute any of the control,
virtualization, or operating system applications described above.
The electronic system 2500 may be a computer (e.g., a desktop
computer, personal computer, tablet computer, server computer,
mainframe, a blade computer etc.), phone, PDA, or any other sort of
electronic device. Such an electronic system includes various types
of computer readable media and interfaces for various other types
of computer readable media. Electronic system 2500 includes a bus
2505, processing unit(s) 2510, a system memory 2525, a read-only
memory 2530, a permanent storage device 2535, input devices 2540,
and output devices 2545.
The bus 2505 collectively represents all system, peripheral, and
chipset buses that communicatively connect the numerous internal
devices of the electronic system 2500. For instance, the bus 2505
communicatively connects the processing unit(s) 2510 with the
read-only memory 2530, the system memory 2525, and the permanent
storage device 2535.
From these various memory units, the processing unit(s) 2510
retrieve instructions to execute and data to process in order to
execute the processes of the invention. The processing unit(s) may
be a single processor or a multi-core processor in different
embodiments.
The read-only-memory (ROM) 2530 stores static data and instructions
that are needed by the processing unit(s) 2510 and other modules of
the electronic system. The permanent storage device 2535, on the
other hand, is a read-and-write memory device. This device is a
non-volatile memory unit that stores instructions and data even
when the electronic system 2500 is off. Some embodiments of the
invention use a mass-storage device (such as a magnetic or optical
disk and its corresponding disk drive) as the permanent storage
device 2535.
Other embodiments use a removable storage device (such as a floppy
disk, flash drive, etc.) as the permanent storage device. Like the
permanent storage device 2535, the system memory 2525 is a
read-and-write memory device. However, unlike storage device 2535,
the system memory is a volatile read-and-write memory, such a
random access memory. The system memory stores some of the
instructions and data that the processor needs at runtime. In some
embodiments, the invention's processes are stored in the system
memory 2525, the permanent storage device 2535, and/or the
read-only memory 2530. From these various memory units, the
processing unit(s) 2510 retrieve instructions to execute and data
to process in order to execute the processes of some
embodiments.
The bus 2505 also connects to the input and output devices 2540 and
2545. The input devices enable the user to communicate information
and select commands to the electronic system. The input devices
2540 include alphanumeric keyboards and pointing devices (also
called "cursor control devices"). The output devices 2545 display
images generated by the electronic system. The output devices
include printers and display devices, such as cathode ray tubes
(CRT) or liquid crystal displays (LCD). Some embodiments include
devices such as a touchscreen that function as both input and
output devices.
Finally, as shown in FIG. 25, bus 2505 also couples electronic
system 2500 to a network 2565 through a network adapter (not
shown). In this manner, the computer can be a part of a network of
computers (such as a local area network ("LAN"), a wide area
network ("WAN"), or an Intranet, or a network of networks, such as
the Internet. Any or all components of electronic system 2500 may
be used in conjunction with the invention.
Some embodiments include electronic components, such as
microprocessors, storage and memory that store computer program
instructions in a machine-readable or computer-readable medium
(alternatively referred to as computer-readable storage media,
machine-readable media, or machine-readable storage media). Some
examples of such computer-readable media include RAM, ROM,
read-only compact discs (CD-ROM), recordable compact discs (CD-R),
rewritable compact discs (CD-RW), read-only digital versatile discs
(e.g., DVD-ROM, dual-layer DVD-ROM), a variety of
recordable/rewritable DVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.),
flash memory (e.g., SD cards, mini-SD cards, micro-SD cards, etc.),
magnetic and/or solid state hard drives, read-only and recordable
Blu-Ray.RTM. discs, ultra density optical discs, any other optical
or magnetic media, and floppy disks. The computer-readable media
may store a computer program that is executable by at least one
processing unit and includes sets of instructions for performing
various operations. Examples of computer programs or computer code
include machine code, such as is produced by a compiler, and files
including higher-level code that are executed by a computer, an
electronic component, or a microprocessor using an interpreter.
While the above discussion primarily refers to microprocessor or
multi-core processors that execute software, some embodiments are
performed by one or more integrated circuits, such as application
specific integrated circuits (ASICs) or field programmable gate
arrays (FPGAs). In some embodiments, such integrated circuits
execute instructions that are stored on the circuit itself.
As used in this specification, the terms "computer", "server",
"processor", and "memory" all refer to electronic or other
technological devices. These terms exclude people or groups of
people. For the purposes of the specification, the terms display or
displaying means displaying on an electronic device. As used in
this specification, the terms "computer readable medium," "computer
readable media," and "machine readable medium" are entirely
restricted to tangible, physical objects that store information in
a form that is readable by a computer. These terms exclude any
wireless signals, wired download signals, and any other ephemeral
signals.
This specification refers throughout to computational and network
environments that include virtual machines (VMs). However, virtual
machines are merely one example of data compute nodes (DCNs) or
data compute end nodes, also referred to as addressable nodes. DCNs
may include non-virtualized physical hosts, virtual machines,
containers that run on top of a host operating system without the
need for a hypervisor or separate operating system, and hypervisor
kernel network interface modules.
VMs, in some embodiments, operate with their own guest operating
systems on a host using resources of the host virtualized by
virtualization software (e.g., a hypervisor, virtual machine
monitor, etc.). The tenant (i.e., the owner of the VM) can choose
which applications to operate on top of the guest operating system.
Some containers, on the other hand, are constructs that run on top
of a host operating system without the need for a hypervisor or
separate guest operating system. In some embodiments, the host
operating system uses name spaces to isolate the containers from
each other and therefore provides operating-system level
segregation of the different groups of applications that operate
within different containers. This segregation is akin to the VM
segregation that is offered in hypervisor-virtualized environments
that virtualize system hardware, and thus can be viewed as a form
of virtualization that isolates different groups of applications
that operate in different containers. Such containers are more
lightweight than VMs.
Hypervisor kernel network interface modules, in some embodiments,
is a non-VM DCN that includes a network stack with a hypervisor
kernel network interface and receive/transmit threads. One example
of a hypervisor kernel network interface module is the vmknic
module that is part of the ESXi.TM. hypervisor of VMware, Inc.
It should be understood that while the specification refers to VMs,
the examples given could be any type of DCNs, including physical
hosts, VMs, non-VM containers, and hypervisor kernel network
interface modules. In fact, the example networks could include
combinations of different types of DCNs in some embodiments.
While the invention has been described with reference to numerous
specific details, one of ordinary skill in the art will recognize
that the invention can be embodied in other specific forms without
departing from the spirit of the invention. In addition, a number
of the figures (including FIGS. 11, 12, and 24) conceptually
illustrate processes. The specific operations of these processes
may not be performed in the exact order shown and described. The
specific operations may not be performed in one continuous series
of operations, and different specific operations may be performed
in different embodiments. Furthermore, the process could be
implemented using several sub-processes, or as part of a larger
macro process. Thus, one of ordinary skill in the art would
understand that the invention is not to be limited by the foregoing
illustrative details, but rather is to be defined by the appended
claims.
* * * * *
References